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- No such things as bad days, just bad moments
PL 700 II Clair Bros Rising from the Ashes
- Thread starter Peter S
- Start date
Back in business! (I hope)
I believe it was "a flakey solder joint. I was fooled because 3 minutes of compressed air cooling brought the trace back SLOWLY. I would have thought that a bad solder joint would not cause a slow return of the image......however if the bad connection was related to the CRT filament....
Anyway, so far, the scope has passed the toughest test of all; putting the covers back on---this always brings back an intermittent problem for me!
Now, back to the Phase Linears; next, I will attempt to test the LED VU meters in the full complimentary amp without the amp functioning.
I believe it was "a flakey solder joint. I was fooled because 3 minutes of compressed air cooling brought the trace back SLOWLY. I would have thought that a bad solder joint would not cause a slow return of the image......however if the bad connection was related to the CRT filament....
Anyway, so far, the scope has passed the toughest test of all; putting the covers back on---this always brings back an intermittent problem for me!
Now, back to the Phase Linears; next, I will attempt to test the LED VU meters in the full complimentary amp without the amp functioning.
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Nothing earth-shattering but both VU meters are working now. I drove the meter pcb's directly with a Leader signal generator. About 8 VAC got the +3 db segments to illuminate. BTW, all three LED segments above 0 db would flash, I take it this is normal?
Found yet another bad solder joint that kept the +3 db segments of channel B from working initially.
Found yet another bad solder joint that kept the +3 db segments of channel B from working initially.
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There was a pcb eyelet that had separated and broke free from it's circuit trace. A simple wire splint did the trick.
Now for the 'shopping list'. I have received so much valuable information from this forum already, but I would like to field this question;
Should the quasi-complimentary amp be rebuilt as full-complimentary or rebuilt as quasi? (assuming a White Oak PL 36 is available for both)...hope this is not a dumb question, I'm new here!
Thanks again, Peter
Now for the 'shopping list'. I have received so much valuable information from this forum already, but I would like to field this question;
Should the quasi-complimentary amp be rebuilt as full-complimentary or rebuilt as quasi? (assuming a White Oak PL 36 is available for both)...hope this is not a dumb question, I'm new here!
Thanks again, Peter
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Hi Folks;
I am hoping to go 'whole-hog' on the White Oak goodies. I have come to believe rebuilding both as full-complimentary seems to make the most sense. In the meantime, I have some clean-up to do. I want this these amps to look good, even if they don't work! ........kind of reminds me of the wife.
PS; I might have to delete this entry!
I am hoping to go 'whole-hog' on the White Oak goodies. I have come to believe rebuilding both as full-complimentary seems to make the most sense. In the meantime, I have some clean-up to do. I want this these amps to look good, even if they don't work! ........kind of reminds me of the wife.
PS; I might have to delete this entry!
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Above pictured is the bent transformer cover----that won't do!! I had to remove the cover to straighten it. I always thought those covers were stampings, but they are die-cast. These amps are Clair Bros and have huge Zoebel resistors, can/should they be retained in the 'WOPLing' process?
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Peter,
We have already had this discussion on the phone.
The 50 watt 5 ohm Dale RH-50 resistors (in the Zobel network) were used by Clair Brothers because they drove the amps hard into clipping above 8kHz into a 4 ohm load. These Dale resistors have a maximum voltage range of 1285 volts. The TRW BWH's that Phase used (2 ohm ohm 2 watt in parallel) rating was: "dielectric withstand voltage (RMS)": 1000V. Phase also used some TRW PW5 5 ohm 5W resistors. I'm not sure of the voltage rating on these. The Vishay CPF-2's used on the W.O.A. back-planes have a maximum working voltage of 350V. If you use Don Imlay's 700 relay board he is currently using (2) Xichon 2.7 ohm resistors in series (for an effective 5.4 ohms) which have a W.V. rating of 350V / O.V. rating of 600 volts. (NOTE: Don replaced the earlier Ohmite TWW5J4R7E's he was using because of some issues (oscillating - due to some inductance?) he had with them. They had a "dielectric withstand voltage" of 1000V.)
I would hesitate testing any of these amps both channels driven into a 4 ohm load at 20kHz for a given duration of time without the 50 watt resistors installed. Otherwise, you more than likely will blow up the resistors. I have experienced this first hand.
In Ben Duncan's book "High Performance Audio Power Amplifiers" pg 382:
"In amplifier servicing, discovering slightly singed zobel resistors is not unusual. They are best looked at, whenever amplifiers are overhauled; and also after anyone discovers that a faulty console (or preamp or other equipment) has been driving RFup the system. Thoughtful makers will place the Zobel resistors where they can be readily inspected and replaced. Ironically, once the Zobel network is at all damaged, the stabilizing resistance value usually increases, thus the amplifier is all the more likely to go unstable, generate its own RF output, and finish off the burnout."
NOTE: This appears to suggest that the Zobel should be located on the speaker binding posts.
However, Bob Cordell's book "Designing Power Amplifiers" 1st edition pg 226 states:
"......suggests that the Zobel network should be located close to the output transistors."
By the way, there were some later Phase Linear 700 series 1 amps that had the Zobel network located on a pc board screwed to the bottom of the Honeywell meters along with some incandescent bulbs to illuminate the meters.
Installing the Dale 50 watt 5 ohm resistors becomes a bit of a problem when installing Don's board. You would need to mount them somewhere else on the side of the chassis and run some leads to the board.
Without the 50 watt resistors installed, I would hesitate to say that the amp is a Phase Linear Clair Brothers amp. Since that part was required by them. But then again the amp will no longer be a Clair amp with the W.O.A. mods anyway.
The choice is yours to make.
Ed
We have already had this discussion on the phone.
The 50 watt 5 ohm Dale RH-50 resistors (in the Zobel network) were used by Clair Brothers because they drove the amps hard into clipping above 8kHz into a 4 ohm load. These Dale resistors have a maximum voltage range of 1285 volts. The TRW BWH's that Phase used (2 ohm ohm 2 watt in parallel) rating was: "dielectric withstand voltage (RMS)": 1000V. Phase also used some TRW PW5 5 ohm 5W resistors. I'm not sure of the voltage rating on these. The Vishay CPF-2's used on the W.O.A. back-planes have a maximum working voltage of 350V. If you use Don Imlay's 700 relay board he is currently using (2) Xichon 2.7 ohm resistors in series (for an effective 5.4 ohms) which have a W.V. rating of 350V / O.V. rating of 600 volts. (NOTE: Don replaced the earlier Ohmite TWW5J4R7E's he was using because of some issues (oscillating - due to some inductance?) he had with them. They had a "dielectric withstand voltage" of 1000V.)
I would hesitate testing any of these amps both channels driven into a 4 ohm load at 20kHz for a given duration of time without the 50 watt resistors installed. Otherwise, you more than likely will blow up the resistors. I have experienced this first hand.
In Ben Duncan's book "High Performance Audio Power Amplifiers" pg 382:
"In amplifier servicing, discovering slightly singed zobel resistors is not unusual. They are best looked at, whenever amplifiers are overhauled; and also after anyone discovers that a faulty console (or preamp or other equipment) has been driving RFup the system. Thoughtful makers will place the Zobel resistors where they can be readily inspected and replaced. Ironically, once the Zobel network is at all damaged, the stabilizing resistance value usually increases, thus the amplifier is all the more likely to go unstable, generate its own RF output, and finish off the burnout."
NOTE: This appears to suggest that the Zobel should be located on the speaker binding posts.
However, Bob Cordell's book "Designing Power Amplifiers" 1st edition pg 226 states:
"......suggests that the Zobel network should be located close to the output transistors."
By the way, there were some later Phase Linear 700 series 1 amps that had the Zobel network located on a pc board screwed to the bottom of the Honeywell meters along with some incandescent bulbs to illuminate the meters.
Installing the Dale 50 watt 5 ohm resistors becomes a bit of a problem when installing Don's board. You would need to mount them somewhere else on the side of the chassis and run some leads to the board.
Without the 50 watt resistors installed, I would hesitate to say that the amp is a Phase Linear Clair Brothers amp. Since that part was required by them. But then again the amp will no longer be a Clair amp with the W.O.A. mods anyway.
The choice is yours to make.
Ed
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Very good question!
I had to go back and take a look at some of my Clair Brother amps to be sure.
It appears that Phase Linear went to using a .22uF capacitor in place of the .1uF caps they used in earlier amps.
It appears from looking over some service manuals that Phase Linear did use some .22uF capas on 700B's with PL14A boards. All the other pc boards/schematics show a .1uF cap.
I just used a RC cutoff frequency calculator on the internet and it appears that the cutoff frequency is as follows:
5 ohm, .1uF = 318,471.3 Hz
5 ohm, .22uF = 144,759.7 Hz
Ed
I had to go back and take a look at some of my Clair Brother amps to be sure.
It appears that Phase Linear went to using a .22uF capacitor in place of the .1uF caps they used in earlier amps.
It appears from looking over some service manuals that Phase Linear did use some .22uF capas on 700B's with PL14A boards. All the other pc boards/schematics show a .1uF cap.
I just used a RC cutoff frequency calculator on the internet and it appears that the cutoff frequency is as follows:
5 ohm, .1uF = 318,471.3 Hz
5 ohm, .22uF = 144,759.7 Hz
Ed
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Here is a link with some history on TRW BWH series resistors and its replacement SPH series after IRC bought out TRW/TT Electronics:
https://www.tedss.com/LearnMore/Failsafe-Moulded-Wirewound-Resistors#cross-reference
Ed
https://www.tedss.com/LearnMore/Failsafe-Moulded-Wirewound-Resistors#cross-reference
Ed
Mouser has a radial .22uF film capacitor rated for 600VAC (Mouser #598-224PPB102K) at $3.90. Illinois Capacitor, but owned by Cornell Dubilier?
They also have an axial .22 film capacitor rated for 275VAC (Mouser #5984-940C6P22K-F) at $3.62. Nice round Cornell Dubilier cap.
Vishay makes a .22uF Y-type capacitor (will not fail shorted) rated for 300VAC (Mouser #594-2222-338-65224) but it is not stocked.
What does Don use for a Zobel capacitor on the DCP board?
The above are a bit larger than the stock .1uF capacitors but that is reasonable for the much higher AC voltage rating.
BTW, the Dale wirewound 5 Ohm 50 Watt resistors are Mouser #71-RH50-5.0 and cost $9.09 each. Should we get a group buy on these to try and hit a quantity of 100 at $6.06 each (not much of a reduction, but it helps).
They also have an axial .22 film capacitor rated for 275VAC (Mouser #5984-940C6P22K-F) at $3.62. Nice round Cornell Dubilier cap.
Vishay makes a .22uF Y-type capacitor (will not fail shorted) rated for 300VAC (Mouser #594-2222-338-65224) but it is not stocked.
What does Don use for a Zobel capacitor on the DCP board?
The above are a bit larger than the stock .1uF capacitors but that is reasonable for the much higher AC voltage rating.
BTW, the Dale wirewound 5 Ohm 50 Watt resistors are Mouser #71-RH50-5.0 and cost $9.09 each. Should we get a group buy on these to try and hit a quantity of 100 at $6.06 each (not much of a reduction, but it helps).
Sorry Ed, yes I remember our discussion now, I think I may be suffering from information overload. I gather there's a zobel network on the relay board upgrade AND the WO back-plane. I am planning to run without the DC protect relay board, but I have not found instruction regarding the omission of the Zobels on the back-plane.
Check out my Zobel below----I like it and I'm keepin' it.......although the wife said it's nothing to brag about.
BTW, they are wired directly to the speaker terminals and the caps are marked with a large "G" and 2A 224K
Check out my Zobel below----I like it and I'm keepin' it.......although the wife said it's nothing to brag about.
BTW, they are wired directly to the speaker terminals and the caps are marked with a large "G" and 2A 224K
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I already have a good supply of the Dale 50 ohm 5 watt resistors. I had a good stash of them from many years ago obtained from Clyde Yamamoto, Dan Kiefer and Dean Nissen. Add to that the ones I got from Perry that were removed from his amps.
The voltage rating on the .22uF mylar's Phase used was 400V. The .1uF mylars were 100V.
The comment Don has on his 700B relay parts list is "reuse the old cap from B.P.".
Or you can buy what Don also uses which is TDK .1uF 100V metallized polyester film capacitors: https://www.mouser.com/ProductDetail/EPCOS-TDK/B32529C1104K189?qs=Gus83tocK7s8MybqFDhfyw==
Ed
The voltage rating on the .22uF mylar's Phase used was 400V. The .1uF mylars were 100V.
The comment Don has on his 700B relay parts list is "reuse the old cap from B.P.".
Or you can buy what Don also uses which is TDK .1uF 100V metallized polyester film capacitors: https://www.mouser.com/ProductDetail/EPCOS-TDK/B32529C1104K189?qs=Gus83tocK7s8MybqFDhfyw==
Ed
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Yes, I believe they are C8 and C9. Mine was already assembled so I missed the build part. The LS=5mm on those capacitors, so a .22uF higher voltage capacitor such as this .22uF 140VAC Kemet polyester capacitor, Mouser #80-R82IC3220AA60J might just be ideal. At $0.63 each, how can you lose?
I wish I had some of that woven lead insulation that Phase Linear and Claire Bros used.
Ed, you are like a virtual encyclopedia of Phase Linear, we mere mortals are in awe. Thank you ther willingness to share your knowledge.
I wish I had some of that woven lead insulation that Phase Linear and Claire Bros used.
Ed, you are like a virtual encyclopedia of Phase Linear, we mere mortals are in awe. Thank you ther willingness to share your knowledge.
