SPEC-4 Recap with AWM-146 0 and AWH-066 C

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I took my untouched SPEC-4 out of my main system and replaced it with a Claire Bros White Oaks Phase Linear 700 completely rebuilt and upgraded by bonzoro. I'm not sure what I'm going to do with the SPEC-4 now, so I thought it would be a good time to re-cap it, while it is out of rotation.

I have been searching the forum, and I did find a few re-cap lists, but they both have different boards than my SPEC-4 has. The lists have AWM-113 for the meter board, and AWH-065 for the output boards. Mine has AWM-146 0 for the meter board and AWH-066 C for the output boards. The S/N on mine starts with BC = March 1981.

Has anyone already documented the differences between the board numbers listed above or created re-cap lists for the AWM-146 0 or AWH-066 C?

Thanks,
Paul
 
I have a question on mattsd's list. Q11 and Q12 are originally 2SC945. The sub is listed as KSD1616AGBU. Is that still a good sub? I've seen threads indicating that it's not a good choice in other applications, but can't find any notes like that regarding its use in the SPEC-4.
 
Mouser still carries the KSC945C, and that's what I'd recommend to replace an original 2SC945.

I'd also caution about simply jumping in and replacing components 'just because'. Electrolytic capacitors, fine. Zener diodes, OK. Transistors...need to have a reason.
 
Mouser still carries the KSC945C, and that's what I'd recommend to replace an original 2SC945.

I'd also caution about simply jumping in and replacing components 'just because'. Electrolytic capacitors, fine. Zener diodes, OK. Transistors...need to have a reason.

OK, thanks...
Only a small percentage of the SPEC-4 transistors are on mattsd's list, and I had assumed they were on the list because they were problematic in some way.

What about the relays on the output cards, would you recommend replacing those or leaving them if not presently causing problems?
 
I received the parts for this and have started replacing cap's on the meter board.
I always test new parts before installing them, but this time I also tested the old cap's.
I was surprised to find that the ESR of old and new cap's of the same value were very close.
Many of the 37 year old 'lytics even had slightly lower ESR than the new replacements from Mouser.
The old ones also tended to measure a little higher than specified capacitance (some a lot higher).
The new ones were all at or below the specified capacitance (but still within specified tolerance).
Pioneer must have used some high quality cap's in this unit... but it would be a gamble expecting much more life out of them.
 
My AWH-066 C output boards only have C1 and C3 installed.
The boards are screened to take C2 and C4 in parallel with C1 and C3.
Is there any reason to not install all 4 cap's?
All are 100u/80V on the schematic for the older board version.

Is it normal that these lines seem to have no filtering ahead of the voltage regulator?
Transformer/bridge/regulator/ then filter cap's...
 
Is there any reason to not install all 4 cap's?
All are 100u/80V on the schematic for the older board version.
I do not see it being a problem having all 4 of them installed. It is actually better imo.
I can only comment on the documentation that I have for AWH-065, I have no documentation for AWH-066 C
These voltage supplies are regulated

Is it normal that these lines seem to have no filtering ahead of the voltage regulator?
Transformer/bridge/regulator/ then filter cap's...
I am trying to figure out what you are asking
The +/- DCV supply to the o/p bjts on the power amp are not regulated, they run off a un-regulated supply.
The supply to the meter amp AWM-113 comes from the rectifiers, on awr-143 and is filtered by C13,14. It is regulated for the +/-65,+20,-13 V DC supplies.
 
rcs, AWR-193 feeds +/- 90VDC to the meter amp board. Pass transistors Q1 and Q2 on the meter amp board regulate the 90v down to 68v to power the input side of the power amp boards. What surprises me is that there are no filter caps on the 90v side of Q1/2, and only 100uF (or 200uF if C2/4 are populated) of filtering on the 68v side. Conversely, the 70v lines feeding the output transistors have 22,000 uF of filtering right after the bridge rectifiers.
 
Yes I know how it works.
It would not work (regulate DC) if there are no ecaps to hold up the rectified AC. It would drop out of regulation with no ecaps to hold the charge(+/-90V). Show me the schematic/pcb foil of that meter pcb that shows no ecaps. I only have docs for AWM-113 as shown in the service manual that I have.
I do not have documentation for a AWR-193.
I assume a AWR-143 is an older version but it has the same function, it supplies +/-90V unregulated to AWM-113, which has C13,14(330u/100V) as the filters to hold the charge between AC cycles.
 
Sorry, not sure how I missed that on the schematic. Yes, mine does have the 330uF caps on the 90v side...
 
I got this thing back together and hooked it up to my DBT with a 100W bulb. The bulb didn't dim by very much after the initial surge, and the relay(s) chattered like crazy, so I shut it down. Does the SPEC-4 draw too much current at idle to run in series with a 100W bulb?
 
Probably with a 100W lamp, should use at least a 150W, the current draw will depend on the amp bias current settings as well.
 
I bought a 150W bulb for the DBT, but the results are similar. The soft start relays chatter like crazy, even with both power amps disconnected.
Has anyone here successfully run a multi-voltage SPEC-4 thru a DBT using a 150W bulb? Do I need to buy a 200W or larger bulb?

Does anyone have a schematic for the multi-voltage version?
This one has 2 relays between the main cap's. The only schematic I can find is for the US version which has 1 relay.
 
I went ahead and tried a 200W bulb in the DBT, but the soft start relays still chattered.
I did a search and found a post where someone had an M-25 that chattered on DBT no matter what size bulb was used, but worked fine on full line power.
I tried it without the DBT and the chatter went away.

Then I hooked the power amps back up, and now the protect relays do not engage.
I do have 48V coming in to both amps on pins 7 and 9 (which are now jumpered together), but I also have 48V on pin 8 on the amp boards, indicating that Q13 on the meter board is not turning on.
On DC detect pins 12 and 13 of the meter board I have .004V and .025V, so that looks ok.
On overcurrent detect pin 11 on the meter board I have 20.3V. I'm not sure if that is normal or not...


Background: This was working fine for years before I took it out my main system several months ago. I decided to do a recap anyway. I replaced all electrolytics except the main quad, and replaced the protection relays. I bought some of the transistors, but ended up not changing any of them. I replaced the bias pots and set the new ones to the same resistance that the old ones were set at. I replaced the offset voltage pots and set the new ones to the same ratio measured on the old ones. I also pulled all of the output transistors and reinstalled them in their original locations with fresh heatsink grease.
 
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