So, here I go. Phase Linear 400

VSAT88

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#1
Hi, she was a working amp until I got scarred by some folks who said I was using a time bomb. Might have been true as the filter caps were stock and no bias readings were ever took (by me anyway). She had almost no DC offset in one channel and very little (well within range) on the other. I played it many many times in fact off and on for several years without any trouble whatsoever. I read on line a lot of differing opinions about it and one that made sense to me was that all the OP TX should be the same. I read the service bulletins and what I read said so as well. I decided to check a few things and found that the OPT were not all the same so after that I decided to replace a few things and add a few things. I bought the new filter cap set from White Oak. I bought the DC relay kit from Mr. Don and put it together with a parts order from Mouser. I called myself following the instructions exactly. I made another order before from Mouser to cover all the lytics (and only the lytics) for the main board/driver board. I installed them all myself of course. I put new silica under each OPT with wakefield in between each, not too little, not too much, just right. I checked all the resistors and found them to be well within range except a for a few and when I found those few in a set of four were a bit out I replaced all four. Some of this was tedious work for me as I am no longer a young man and I cannot see as well as I use to. I tried to do my best. I am going to post some pics here and if needed I will post more of whatever is asked. I hope you find my photographs good enough to see everything well. Now, the problem or may well not be a problem, I do not know. After all the work (including a new bridge rectifier by the way) when I bring it up on the DBT/veriac the bulb pulses. I stopped then and decided to ask for help. Yes, when I start turning the veriac up with the amp plugged into the DBT the bulb goes really bright then back to dim, really bright then back to dim. I have never encountered something like that before so now I ask kindly for your help. Jim. 001.jpg 002.jpg 20170425_121211.jpg 20170426_211220.jpg 20170429_234122.jpg 20170430_001638.jpg 20170503_231621.jpg 20170503_234554.jpg 20170504_001125.jpg 001.jpg 002.jpg 20170425_121211.jpg 20170426_211220.jpg 20170429_234122.jpg 20170430_001638.jpg 20170503_231621.jpg 20170503_234554.jpg 20170504_001125.jpg
 

VSAT88

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Sorry folks.

looks like I do not know how to use the upload images feature well. Duplicate images. Please excuse, remove or tell me how to remove if it is an issue. My bad.
 

VSAT88

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Yes, it seems like it did. In order to tell you for sure I would need to hit the shop. It has been a long time since I fired it up. Cannot believe you answered so quick !
 

laatsch55

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looks like I do not know how to use the upload images feature well. Duplicate images. Please excuse, remove or tell me how to remove if it is an issue. My bad.
Not a problem, don't sweat it...
 

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Yes, it seems like it did. In order to tell you for sure I would need to hit the shop. It has been a long time since I fired it up. Cannot believe you answered so quick !
We aim to please. Won't be on much longer tonight though, 5AM comes early...
 

VSAT88

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I will do whatever you instruct me to but I am not in a rush. If you have time I will take any instruction you may offer and post back the result. Thank you.
 

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#8
You do have a problem with the 909's and 2SD555's in the same channel, not that that's your problem with a bright bulb, but does need to be addressed at some point.
 

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#11
What happens when you isolate the DC protect board from the rest of the amp? Or have you done that? Was there no connection to the speaker posts during this startup? Did you assemble the DC protect board yourself? Or was it preassembled? I notice some caps missing on the DC protect board...
 

VSAT88

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"What happens when you isolate the DC protect board from the rest of the amp" ? Not sure what you mean by that if you mean taking out the relay and trying that way I do not remember doing so. There were no connections to the speaker posts during startup, no dummy loads either. I Did assemble the DC protect board myself . Looks like I goofed ??
 

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#13
Well, that depends, did the kit have some .10uf/100 volt poly caps for C3, C8 and C9?
 

VSAT88

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At C9 and C3 on the protect board right ?. That could be the whole problem could it not ? I will check my parts list and see what I missed if that is the way you say I should start...Willing here to listen !
 

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#16
Yes on the DC protect board. C3, C8, C9. When Don first started selling these DC protect kit we would harvest two of those caps off the original Zoebel network on the original speaker posts.

You changed and/or replaced a lot of things at one time, this might take awhile.

Those caps are in series with those two big resistors on the board, and if they are left out, the resistors should have no effect without the caps. Have you put a meter on the speaker outs to check offset during startup?
 

VSAT88

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You are certainly leading me in the right direction here ! States plainly in the "Phase Linear 400 Relay Parts List from Mr. Don.

C3, C8, C9 Qty 3. .10uF Re use cap from old R/C network on binding post
 

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#19
Yep, you have the same parts list I do....Did you install C3 only and leave C8,C9 empty?
 

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#20
No Sir I have not. As soon as relays started clicking and lights started flashing I put er down for a later date.
OK, but you are sure it cycles bright/dim more than once? And all fuses are still intact?
 
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