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  #61  
Old 04-27-2010, 04:07 PM
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Phase Linear Series II faceplate

Quote:
Originally Posted by Glen B View Post
Sure, no problem. Its going to be a few days, due to a busy schedule.
Hello Glen,

Before going for disassembly of my P/L amp to show the original faceplate to the engraver, do you have by chance its precise dimensions? Or maybe you know someone who has them?

The service provider asked for preliminary description of the job to be ordered and I tried to reflect the panel sizes by measuring and converting metric results into inch system, but not sure I did it right - please see the picture encl.

Many tx for your advice!
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  #62  
Old 04-27-2010, 10:02 PM
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I'm sorry I don't have dimensions. I have a PL 400 II. The faceplate is very easy to remove. Just remove the four nuts holding the handles and that's it.
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  #63  
Old 04-28-2010, 12:28 AM
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releone 71,
I think that a series I with a PL14A driver board capped with Panasonic FC's for C11,15, and 16, Nichicon KZ for C3, and ELNA SILMIC II's for C6 is the best sounding combination for any of the 400's. An interesting sidenote, it did NOT seem to make a sonic difference whether the outputs were XPL 909's, FPL 909's, 2SD555's, MJ 15024's or MJ21196's. I finally got my hands on some RCA 1B05's this week and will try them also. And to make matters more subjective, the original RCA 410 drivers "sounded" the best. Also tried some XPL 910's and some MJ 15011's as outputs with the same results. Other drivers tried were MJ 1800's, MJ 2741's, MJ15024's and MJ 21196's. The phonomenal difference came after that combination of caps.
It brought all of my PL stuff pout of the "harsh" territory to the " smooth" neck of the woods. Price of the upgrade? $3.12.
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  #64  
Old 04-28-2010, 03:29 AM
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Quote:
Originally Posted by Glen B View Post
I'm sorry I don't have dimensions. I have a PL 400 II. The faceplate is very easy to remove. Just remove the four nuts holding the handles and that's it.
Yes, I know :-)... It is easy indeed. Don't want to do it now though. I am in a pre-quote stage and the guy asked me to send some indicative description of the project scope by email to come back with a rough price. What I have should be enough then...
Again, thank you Glen.
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  #65  
Old 04-28-2010, 09:09 AM
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Originally Posted by laatsch55 View Post
releone 71,
I think that a series I with a PL14A driver board capped with Panasonic FC's for C11,15, and 16, Nichicon KZ for C3, and ELNA SILMIC II's for C6 is the best sounding combination for any of the 400's. An interesting sidenote, it did NOT seem to make a sonic difference whether the outputs were XPL 909's, FPL 909's, 2SD555's, MJ 15024's or MJ21196's. I finally got my hands on some RCA 1B05's this week and will try them also. And to make matters more subjective, the original RCA 410 drivers "sounded" the best. Also tried some XPL 910's and some MJ 15011's as outputs with the same results. Other drivers tried were MJ 1800's, MJ 2741's, MJ15024's and MJ 21196's. The phonomenal difference came after that combination of caps.
It brought all of my PL stuff pout of the "harsh" territory to the " smooth" neck of the woods. Price of the upgrade? $3.12.
Good to know, anyway I have a '79 700 Series Two (PL36 board) and the electrolytics are just four. I usually replace with Nichicon because Mouser has a large inventory of that brand though I will give a try to the Silmic one day or another. Thanks for the suggestion.
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Old 04-28-2010, 12:28 PM
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Phase Linear 700 Series II - restoration guidelines

Dear All Phase Linear Friends,

I probably won't be very 'eccentric' to say that Audiokarma is just a perfect place to find so many great solutions while repairing our valuable, certainly in terms of emotions, even most rare audio systems. I’m a strong believer in Phase Linear (P/L) heritage in power and pre-amplification. The brand history speaks by itself... Still if someone who lives far from any experienced P/L service (my case) wants to perform some required renovation works for the 700 Series II amp ( i.e. is able to do it), many important and undocumented tweaks are quite difficult to find even here. They are well spread around and despite educational benefits in looking for them in all various threads, it takes long time to identify the key ones.

That is why I thought to put together some major recommendations based on numerous P/L related AK threads, most often coming from D3imlay – many thanks Don!

Main purpose of the list below is to help in planning and performing the restoration of 30+ years old P/L 700 series II amplifier, and certainly not to re-engineer the gear. Replacing a vast number of components, that were working well so far and are not specifically exposed to aging, is not recommended. No doubt the temptation to try some great advice is in everyone of us – after all you decide at your own risk …

1) GENERAL RULE: Use extreme caution while performing any replacements/upgrades due hazardous voltage presence in P/L 700 II power amplifier. Be sure that before starting any replacements the line cord is unplugged and power supply caps are discharged. Strictly follow ALL check-up and repair procedures as written in P/L 700 II Service Manual and subsequent service bulletins. Wear safety glasses while taking data from powered circuits and soldering. Before you start it is mandatory to have required equipment by the factory service manual (covered in later posts) and necessary tools - for toolkit recommendations see this thread for help: http://www.audiokarma.org/forums/sho...d.php?t=187673.

2) For powering up, before the check-up procedure starts, or/and for performed modifications testing, use light bulb test set (http://www.audiokarma.org/forums/sho...d.php?t=187673). Start with a 40 or 60 Watt bulb. Step up to 100 Watt or 200 Watt as your confidence builds. You can't have a load connected when you use the bulb. The amp puts out several volts DC as it starts up. If a load is attached, the bulb limits the current, as it is supposed to, and the AC input never gets above 30-40 volts. Use of variacs only will not limit the current and may burn all the output transistors (painful when you just replaced them…). If you still want to use the variac only, change AGC fuses to much smaller values to control excessive current.

3) Outputs and drivers should be reinstalled even if not destroyed. The reason are rubber insulators causing failures in time when overheated. If the amp had silicon pads on the outputs always get new ones - never reuse them! Don't over-tighten while mounting transistors. If you use mica insulators as preference, go easy with term compound grease. Keep it out of the sockets. Heat sink plates must be well cleaned before re-installation of outputs and drivers.

4) Following P/L service bulletins, output transistors in each channel should ALL be of the same type (e.g. MJ15024 or MJ21196 for quasi-comp. stage, or MJ15024/25 / MJ21196/95 respectively for full comp. stage). MJ211** are probably today’s most advanced high power TO-3 outputs and have higher SOA than MJ150**. In 700 Series II full complementary amp, the drivers and output transistors are the same. For example – the driver for the MJ15024 output transistor is a MJ15024. Same comment for the MJ15025 (PNP match for the MJ15024). In other words DO NOT mix different types of output transistors in a single channel. The previous statement is very important when doing service or repair work – not only with P/L equipment, but any kind / brand of amplifier. In 700 Series II quasi complementary amp there are obsolete RCA410 as drivers. Leave them, if not shorted, for better stability and sound (subjective impression). Last but not least, avoid buying the output transistors from unknown sources, counterfeited ones are often found. They won’t be of any use in 700 Series II severe working conditions.

5) P/L 700 Series II driver board (PL36) requires some closer attention. There are components that over last decades could loose resistance /capacitance desired characteristics or get open, even impacting other elements, not to mention about shorted diodes or signal transistors. To simplify our list, it is assumed that the PL36 and PL37 (display) boards worked OK before the restoration works had started and only outputs were actually replaced.

6) The resistors to consider for replacement, as they may drift from heat and age, are:

-> R1, R2 = 7.5K/5W 5% (these dropper resistors get so hot to even discolor the PCB card and affect nearby parts as well),
-> R101 = 7.5K/2W 5% (applicable per other channel too),
-> R103 = 2.7K/0.5W 5% (applicable per other channel too),
-> all power outputs emitter resistors = 0,33Ohm/2W (if you replace them, pick high grade with 1% tolerance 3-5W, coated wirewounds are nice).

7) In order to cure possible oscillations, usually after you replaced power outputs, the capacitors a 22~47pF usually work well to damp out any such tendency (see specific P/L service bulletin on the issue). The factory recommended 150~270pF value might be too high, and can cause high frequency slewing at high output power. Ceramic or silver mica types are recommended with at least a 100-Volt rating.

8) Replacement of all electrolytic caps on the driver board is highly advisable. Try to stick to high class brands designed for audio applications (e.g. Panasonic FC, Nichicom KZ, Rubycon ZA, ELNA Silmic II) - subject for sound tests and above all own music preferences. This upgrade most probably influences how your amp will eventually sound like. Some P/L fans say that ELNA caps are slowing and soften the music you hear, so good to listen for instance to mellow jazz. Sometimes not desired when you like 'rocking the house'… My own choice were Nichicon Muse and Rubycon high grade, but the latter are hard to find, especially for 100V (watch out for fakes!). Interesting comments on recapping can be found here by Arkay, see post #4: http://www.audiokarma.org/forums/sho...d.php?t=287093. Very informative post #15 by Echowars on matching caps' voltage is here: http://www.audiokarma.org/forums/sho...58#post2637358. No need to exaggerate though - please bear in mind that Phase Linear power amps are direct coupled and have no electrolytic caps in the signal path. So the replacement is a rather a precaution to avoid caps aging problem in the power supply, feedback network and bootstrap circuit (last remarks thanks to Dean & Ed).

9) The Op-Amp IC LF356 replacement with LF351 is recommended by the factory, so is the replacement of R1, R2 from 2.4K/5W to 7.5K/5W (the LF351 op-amp has better specs and helps with turn on/off thump). I don’t want to open a separate debate on whether LF351 is fine for front-end applications or not, in view of many options available these days. The op-amp in the P/L design had one purpose: to provide high gain and it was used to replace a traditional differential input pair - much more refined solution known from P/L 400-700 Series I. This had few advantages back in the 70's: all the transistors inside the op-amp could be closely matched (important for a differential amp) and production / testing was more efficient since matching of transistors was no longer necessary. LF351 is not at all a bad op-amp. So, let’s simply leave it as is. However, for All who like experiments it is highly recommended to put on IC 8-pin socket. Remember - the traces on the board are aged and therefore very delicate. The use of BB OPA134 op-amp as direct replacement to LF351 might be sound quality beneficial upgrade. For the music I personally like, and my whole audio setup, they work just fine – not too much ‘dark’ as some LM or AD IC’s enthusiasts may say… Besides for the other IC units you would need to make some power supply improvements (e.g. constant current source, higher voltage supply: >15V) and we were not here to re-engineer the P/L great amp, right?

10) Regardless whether you stay with LF351 or not, there are some common practices you may want to consider for the op-amp working conditions improvement. First is to add decoupling 0,1uF (e.g. per 100V) high grade film type cap on the +/- 15V rail supply and mounted directly on the supply pins for each op-amp (diagram attached to the thread #74, the solution helps in removing power supply noise and possible distortions at high frequency). Second would be to add 4,7uF/35V electrolytic cap ('reservoir') in parallel to each D1, D2 Zener diode. Be careful though - too much capacitance increases the turn-on thump.

11) Power caps are absolutely worth of replacing. They also strongly influence the sound when got dried over the years. Sometimes they may well become a source of hum. With the new ones go for twice the capacity than original - ca. 20.000uF @100V at minimum - you can find per 160V at small price difference = better (The originals were 9800uf @100V and they run right around 100V. With caps you buy today you don't get the headroom like you did 20 years ago...). The power supply caps testing: check if they have less than a few hundred mV of ripple at idle, at full load it will be slightly over 1V. Don’t buy power caps older than 3-5 years of shelf storage, if you don’t have time for reformatting them. Watch the cap size to avoid additional mounting problems. Before you begin, remember to discharge the power caps (a resistor 10-25 Ohm/10W would help)!

12) If you increase the power cap capacitance from original value of 9.800uF to say 20.000uF, you need to take into account the higher stress on your bridge rectifier. Some P/L owners decided therefore to upgrade it for >35A/400V units. In addition bypassing each diode by 0.01uF/1000V cap (ceramic or mylar HQ) will help to cure against RF unwanted interferences. BTW, you need to check the presence of C112=0.22uF/400V as no longer needed. Bypassing filter caps with two mylar caps 0.1-1uF/600V can be considered if you go for larger power capacitors. It will improve the ESR at higher frequencies. For 20.000uF cap, with low ESR, ‘computer high grade’ type, etc., etc. - you may not bother, probably.

13) Final review of the PCB card from the traces side is maybe a simple advice, but very important at the same time. Apparently over time the PCB material gets more ‘fatigue’ and you need to resolder anything that looks questionable. Cold/open solders are most time consuming cause for the amp malfunctions to find.

14) In the end bias setting is always needed. See related procedure in the P/L 700 Series II service manual. Here is a short wrap-up - not to forget about the step. So, when all the changes to your amp are finally done, use the bulb testing device to start the amp with no I/O connections. When successful, use a voltmeter to measure Voltage across the zener diodes. You should see +/- 15 VDC. Typical is around 14.5 VDC. Then with full input voltage check for about 300~350 mV DC on the 10 Ohm/0.5W resistors on the output buss (R109). Adjust the pot (R107) for the corresponding channel as needed. Recheck in ten minutes. Verify if less than 30 mV. Be careful when taking data. A slip of the probe will cause major damage. Insulate the probe tip with tape or heatshrink. Always wear safety glasses.

15) When you performed all the upgrades, installing the output protection circuit is to be seriously considered to eventually save your precious loudspeakers... There are few options for P/L 700 Series II to follow and at AK you can easily find them (D3imlay). Otherwise just Google the topic, and for EU P/L amp owners there is a module I know 'made in the Netherlands', but also for instance another fine one from Tasmania (...). But one common mistake here is to forget about reconnecting the RF circuit (C108 & R135) from speakers’ terminals to the protection unit inputs. You will experience oscillation problems if you forget the precaution. Very useful educational case story for deploying the output protection for P/L 400 amp is found here: http://www.flickr.com/photos/watts_a...7604339152710/ (by Don Imlay).

16) To conclude, a piece of electromechanical advice: replace all RCA inputs and speakers posts for something 'more sound neutral' than it is today. A variety of solutions can be found in other AK threads. Also don’t forget about the power cord – better to replace the old one if suspected condition. It should be non-polarized and not wall socket grounded (even for EU standards) – otherwise very likely hum problems appear. Keep the 'earth ground' connected closely to your source (CD/DAC/Pre-amp).

I refrain on purpose from touching the amp rewiring topic in more details. There is an issue here, known to all P/L users. In P/L 700 Series II amp the RCA input ground is correctly tied to the input ground of the amplifier's input circuits. Then the right channel's speaker ground is directly tied to the RCA ground... So ground current flowing into the right channel speaker ground is injected into the 'quiet' input ground (unwanted loop deteriorating the sound). Grounding is critical to both stability, measured performance and the amp sound quality. Star topology should be observed. At least one ground wiring should be added between a solid copper bare inside your amp and the common point on the power supply caps. Again, see Don valuable recommendations on that.

I welcome all additional remarks and corrections - nobody is perfect ;-)...

Good luck with your projects!

May Force Be With You....

Last edited by P.L.F.; 06-07-2010 at 07:45 AM. Reason: corrections:OpAmp decoupling, remarks on recapping (signal, PS)
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  #67  
Old 04-29-2010, 10:24 PM
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PLF,

I think you've just about said it all. I would like to add an observation for users of the light bulb startup. You can't have a load connected when you use the bulb. The amp puts out several volts DC as it starts up. If a load is attached, the bulb limits the current as it is supposed to and the AC input never gets above 30-40 volts.

There is a way cool mod that I used to do on II's for pro sound apps. We had the front panel milled to allow the fuse holders to be brought out in front. Separate fuses were used for each channel making a total of 5. A toggle switch was added also. This may be worth consideration if new panels are going to be made. I may have a drawing showing dimensions. We changed C106 to about 300pf as I recall. This rolls off the HF response and saves HF drivers. Remember, this was for pro use.
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  #68  
Old 04-30-2010, 05:10 AM
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Quote:
Originally Posted by d3imlay View Post
I think you've just about said it all. I would like to add an observation for users of the light bulb startup. You can't have a load connected when you use the bulb. The amp puts out several volts DC as it starts up. If a load is attached, the bulb limits the current as it is supposed to and the AC input never gets above 30-40 volts.
Thank you Don,

Your kind remark is already incorporated to the latest 'release' of the amp quick restoration guidelines. Great you had a moment to look at them.

Best regards, Przem
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Last edited by P.L.F.; 04-30-2010 at 12:56 PM.
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  #69  
Old 05-01-2010, 05:59 PM
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Quote:
Originally Posted by P.L.F. View Post
10) Regardless whether you stay with LF351, or not, there are some common practices to consider for op-amp working conditions improvement. First is to add decoupling 0,1uF high grade film type cap on the +/- 15V rail supply. Second would be to add 4,7uF electrolytic cap in parallel to each D1, D2 zener diode. Be careful though - too much capacitance increases the turn-on thump.
P.L.F.,

I've taken good note of your tips when restoring a PL amp and I've placed an order for the proper parts (caps, rectifier, etc.). Anyway, I'd wish you to better explain the point #10). Which voltage for the 0.1 and 4.7mF caps? Will you be so kind as to explain also where to put the 0.1 cap on the PL36 board exactly? Do you mean a single cap across the inputs marked as B+ (red) and B- (black) in the diagram 2-3 (page 8) of the service manual or elsewhere along the rail supply?
I'd like also to replace the power devices by myself but I need the proper equipment. Therefore I'm planning to purchase a basic signal generator and oscilloscope on the purpose. Any suggestion regarding the brand/model? That would be useful for my other amps too. Thanks.
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  #70  
Old 05-01-2010, 08:23 PM
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Quote:
Originally Posted by d3imlay View Post
The outputs are wired in parallel so that they share the heat dissipation. The amp will still work, and still put out the same power, but will fail at high volume levels. From the pic, it looks like the outputs have all been replaced with a sub. The outputs are fairly inexpensive. The service manual, which I have on PDF, is very good. You really should have an oscilloscope and signal generator to check out this amp.

The 400, unlike the 700B, did not come with a power switch or level controls. I've got some info on my web site. At this time I use MJ21196's for outputs.

Phase Linear info

See the service bulletins.
Your the guy I need to talk to! Your Phase Linear speaker relay looks very much like the relay cuircut in my SAE amps, and I know that relay looks like the same relay that they use, can you let me know how to get them?
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Old 05-01-2010, 09:09 PM
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Wow I can't beleive I missed this thread, as I am newby to vintage audio and fairly new to AK. That being said I have purchased a few Phase Linear items to fill one of my audio racks and that being said I have a few with problems. The first one that I want fixed is my PL 700 series II amp. it looks good, clean inside no visible problems but it blows fuses and has a mix of different power transisitors on it. Looks like the main caps are fairly new. I almost ordered that kit on ebay to replace all the main transistors but to be honest is that something I want to take a gamble on? I know I can take out the old ones and put some new mica insolators and install the new ones but setting the bias and all I only have a multi meter. I did buy the kit for all new capacitors for the driver board but have not touched anything yet. I am using my PL 400 and a SAE 502 right now to power my speakers. I have quite a few pairs of speakers, mainly Infinity's, QLS-1's RS-1b's, RS-1a's, Kappa 9, Kappa 8's and a pair of Phase Linear III's. I need more power so I want to fix this PL 700 amp and buy another one so I can have a pair for bi-amping the big Infinitys. One other question since everyone is so informed here. The Infinity RS-1b's and RS-1a's require two amps one for the bass towers, and one for the mid-hi towers. The Infinity active crossover that comes with these speakers is very specific about the amps being phased correctly. It does have a switch on the back for inverting the phase but if you don't know if your amp is phased it will cause the amp to go into oscollation and blow the amp and damage the speakers. So does anyone know if the Phase Linear amps are phased correctly or Phase inverted? I would love some suggestions on getting my amp fixed, by someone who really knows how to fix them and understands that these are going to be use on Watkins Dual Voice Coil drivers and speakers that sometimes have pretty low impedences. I must say I have had no problems with the little PL 400 II that I am currently using to drive the QLS-1's with now but I am afraid to use them one the RS-1b's until I know about their phase orientation. Right now I have been limited to using some Crown amps that I have, that being said the Crown amps will be just fine for the bass towers but I think I like the musical sound of the Phase Linear amps on the mids, and hi's more than the Crown amps. This thread has been very informative, and I thank everyone for all their help.
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Old 05-02-2010, 06:33 AM
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Quote:
Originally Posted by Ken Boyd View Post
The first one that I want fixed is my PL 700 series II amp. it looks good, clean inside no visible problems but it blows fuses and has a mix of different power transisitors on it.
My '79 700 II is the same (it was a disco mule which saw some blown transistor during its career) but it works good at the moment because it was serviced by the precedent owner. Anyway, it is my intention to replace the power devices with transistors of the same type as suggested by the service manual. The choice nowadays falls on the complementary MJ21195/21196 (10 each) from ON SEMICON which are similar to the old MJ15024/15025 but have better performance in the safe operation area. You can purchase them matched from the guy who sells on eBay the repair kits for PL or from D3Imlay (Watts Abundant). Obviously, if yours has a quasi complementary output stage you will have to purchase only 20 MJ21196 (NPN type) or modify the output topology into a complementary as suggested in the PL service bulletins.
Regarding the blown fuses it is strongly recommended to refer to the service manual (if you need it, PM me). Take a look at the troubleshooting section and perform the tests as suggested there.
What can you say about your transistors? If you want to replace them all with new devices I could consider the option to purchase them all "as they are" and go for a philological restoration of my amp. I need Motorola TP9054 (MJ15024) and DB15025 (MJ15025), possibly produced in the late 70s (mine are dated '79). Please, PM me in case.

Quote:
Looks like the main caps are fairly new.
If the main caps are new you will have no need to replace them. Anyway, if they are the original 9,800mF you'll better replace them with new devices and double the capacitance. See point #11) in the P.L.F. post. I personally purchased a pair of 22,000mF Vishay low ESR computer grade from Mouser and a new bridge rectifier to compensate the higher stress. Add also bypass caps to the rectifier and the main caps (point #12)). Take good care in choosing the new main caps not only from the value but also from the diameter and spacing of the contacts. A little tolerance (+/- 1") is admitted for the lenght.

Quote:
I almost ordered that kit on ebay to replace all the main transistors but to be honest is that something I want to take a gamble on?
That kit (the whole kit containing transitors, diodes, caps, resistors) is good because you have all the parts at once for future repairs of the amp. Anyway, as suggested by D3Imlay, if the parts in the driver board are OK there's no reason to replace them until they work. Take care in replacing only the main resistors (see points #6 and 8) and the 4 electrolytics caps with audio grade devices (you will find them all in the kit). Be aware the main resistors (R1, R2) have different value in case your unit has the early LF356 ICs or the late LF351 (2.4kOhm or 7.5kOhm/5Watt). Therefore take a look at the small ICs in the upper side of the PCB and order the proper parts in that kit. It is recommended anyway to go for a couple of new LF351s which reduce the bump when turning off the amp.

Quote:
I know I can take out the old ones and put some new mica insolators and install the new ones but setting the bias and all I only have a multi meter. I did buy the kit for all new capacitors for the driver board but have not touched anything yet.
When replacing the power transistors use self lubricant insulators instead of messing with the micas and thermal compound. Take care only in avoiding to overtighten the screws of the TO3 cases, otherwise the insulator will break shorting the transistors to the chassis of the amp. Just screw them down using your fingers until they stop over the case surface, then tighten them gently with the wrench. A 90░ turn will be enough. Anyway, refer to the service manual for the operation and follow the test procedure described there. You will need a signal generator and an oscilloscope though. I thought they would be useful also for servicing my other amps so I'm going to purchase them. There are several good occasions on eBay for a few bucks. I'm going to purchase also a variac which is useful both for servicing the PL and when turning on equipment unused from several years. In this case the risk is to short electrolytics and tubes.

Again, whether you need the service manual or wish to get rid of your transistors PM me. Good luck!!!

Last edited by releone71; 05-02-2010 at 07:25 AM.
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  #73  
Old 05-02-2010, 08:20 AM
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Quote:
Originally Posted by Ken Boyd View Post
Your the guy I need to talk to! Your Phase Linear speaker relay looks very much like the relay cuircut in my SAE amps, and I know that relay looks like the same relay that they use, can you let me know how to get them?
The relay is Mouser P/N 677-PCLH-204D1S.
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  #74  
Old 05-02-2010, 08:24 AM
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P.L.F. P.L.F. is offline
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Posts: 152
Quote:
Originally Posted by releone71 View Post
P.L.F.,

Anyway, I'd wish you to better explain the point #10). Which voltage for the 0.1 and 4.7mF caps? Will you be so kind as to explain also where to put the 0.1 cap on the PL36 board exactly?

I'm planning to purchase a basic signal generator and oscilloscope on the purpose. Any suggestion regarding the brand/model? Thanks.
Releone71,

Referring to the point #10 there are indeed two recommendations to consider:

a) rail-to-rail decoupling to help in removing power supply noise and distortions at HF via 0.1uF high grade film cap - here the voltage is not an issue as we speak about -/+15V DC rails, so you can use most common, say 100V type for instance. For more details please see the attached diagram.

b) bypassing the two Zener diodes by an electrolytic cap 4.7uF - again, you should expect about 14.5V DC on those diodes, so 25V-cap as a min. should work fine. This solution helps in more stable working conditions for the IC op-amp (reservoir capacitor role).

For test equipment you could have a look at these topics:
- oscilloscopes: http://www.audiokarma.org/forumsshowthread.php?t=236720
- audio generators: http://www.audiokarma.org/forums/sho...udio+generator

Mine are: OWON PDS5022S (ebay.it ;-): http://cgi.ebay.it/OWON-7-8-color-LC...-/170380118555)
and for audio signals: TENMA 72-505 audio generator (http://www.mcmconnect.com/tenma/product/72-505/).

Ciao!
Attached Files
File Type: pdf PL700II IC decoupling options.pdf (29.1 KB, 47 views)
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  #75  
Old 05-02-2010, 08:28 AM
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d3imlay d3imlay is offline
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I never reuse the silpads as a safety precaution. I got a deal on about 10,000 of them so I have no reason to reuse them. Never force the screws. It is possible to cross thread them. I use an extended nut driver held with thumb and index finger. When the nut driver spins in my fingers the screw is tight.

I'll confirm that they're not phase inverted. If they were that would seem to contradict the name.
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