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Post by jukenorman on Jul 22, 2023 15:44:42 GMT
Clearly something is far wrong! Since you had previously said that one channel was functional, are you sure your meter is OK?
Norman.
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Post by prime on Jul 22, 2023 16:20:14 GMT
I have three multimeters all same result, installing a board in the channel that didnt work, i can not get any voltage at R25 either board, in the slot with the good channel on one of the boards i can set R25 to 0, but the lowest i can get R33 is 2.7 The other board i can not get the numbers below 68 on R25 either way and never get - voltage. both boards test out pretty well exactly the same on all components except for PEC8 dont know exactly how to test it. ps the resisters get hot when connected the bad channel so i know some power is getting there
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Post by jukenorman on Jul 22, 2023 16:59:16 GMT
It does seem strange that a functional board fails adjustment? It would not surprise me if PEC8 was faulty, I'm not sure about Q7 though. There is already a thread on the forum about PEC8, I'm surprised you didn't find it when you carried out the search for information on your amplifier that I suggested you do!
Norman.
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Post by prime on Jul 22, 2023 17:08:14 GMT
I did see info on the PEC8 seems difficult to get and seems to cause a machine gun affect in some cases, I was hoping through testing to rule it in or out, could that affect the faulty board and also stop the good board from allowing the R33 from adjusting properly. I will try and see f i can get replacements. Any chance you have either schematics on how to produce that chip or know where to get one, i tried the Netherland site and could not find it, i saw a video on you tube about someone getting them from Germany, he stated he will list supplier at the bottom of his page but never does.
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Post by jukenorman on Jul 22, 2023 19:16:12 GMT
The schematic is already posted in the PEC8 thread.
Norman.
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Post by prime on Jul 22, 2023 23:36:31 GMT
Hi guys i thought diodes were like switches measuring one way or allowing currant only one way. Are AVC diodes different i see 1-4 measures the same voltage each way also i notice the bridge diode shows short each way. So is this normal. All tests on diode position
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Post by jukenorman on Jul 23, 2023 9:46:40 GMT
It's very difficult to carry out meaningful tests on an encapsulated circuit like that PEC because of parallel circuits etc. Though I suppose showing a dead short wouldn't be good news! You would also be able to compare readings with a known good one so you would get some indication by checking the other driver board. I think there is enough info on the PEC8 to be able to make them if you fancied having a go?
Norman.
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Post by prime on Jul 23, 2023 14:17:29 GMT
Again i see i have been too vague, the resisters are not on the driver board but on the tone board, also the shorted resister is not on a board it is by itself as per photo bellow, i circled the 4 resistors and part circle on the shorted one. The 1-4 are called AVC diodes and the shorted one is called a bridge. The parts list does not list values, how would i find that. thanks pete  |
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Post by jukenorman on Jul 23, 2023 15:27:24 GMT
Hi Pete,
No wonder we get confused! A resistor is not a diode! CR1 to 4 are termed AVC diodes and are shown diagramatically on the schematic as two diodes in series and that would be fairly normal for AVC use. If you had to replace any of them, two small signal diodes in series would be fine.
The other item - you must bear in mind that I don't have an amplifier to look at so I have no way of identifying the other item that you have marked. I was only able to identify CR1 to 4 because I can see the idents on the picture you posted. Does that other item have a number ie CR something?
Norman
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Post by prime on Jul 23, 2023 16:09:15 GMT
I cant believe I called them resistors just now, in my earlier post i made it clear it was diodes, the bridge diode has markings upper row 002 lower row 801, also you call the 1-4 diodes signal diodes on those i get 1.9 v black on cathode red on anode and 1v black on anode red on cathode is that normal? the bridge diode i get ov either way , all testing on diode setting. If i test the bridge diode using continuity setting same thing zero v and beep
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Post by jukenorman on Jul 23, 2023 17:19:17 GMT
Pete, the markings don't mean much to me. If you've checked that it's a bridge diode in the parts list, you must know its ident like CR19 or something - that's what I would need to check the schematic to see what you could use as a replacement. The AVC diodes will be two or maybe even three diodes in series in a single package. That is to raise the forward bias voltage drop which is about 0.6V for a silicon diode. I'm not familiar with your meter so I don't know under what conditions it beeps.
Norman.
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Post by prime on Jul 23, 2023 18:11:14 GMT
The meter is a fluke 115 as per photo and beeps in diode or continuity mode when zero resistance is found, Im not sure of the number of the bridge diode it not marked but i believe its CR 18 that lists as 1 amp bridge diode. photo below showing it clearly. postimg.cc/gallery/c0SvGbk |
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Post by jukenorman on Jul 23, 2023 19:25:57 GMT
Definitely not CR18 which is a composite bridge rectifier so would have four terminals. Can you trace out where it connects to or anything else that might identify it? Difficult to tell from your picture but does one side go to ground and the other side to a plug? I'm probably very old fashioned but I always check diodes on the resistance scale!
Norman.
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Post by prime on Jul 23, 2023 19:47:10 GMT
I have decided through extensive testing those Diodes are fine, I will need to wait untill i replace the two PEC 8 chips to see if i can adjust boards as per spec and get sound.
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Post by prime on Aug 15, 2023 18:26:48 GMT
Hy Norman, i ended up getting two chips from the Netherlands, I installed both of the new PEC-8 chips, I set the R33 on both 52265-A drivers to minimum, i set the R25 to the centre. I installed one of the boards, set amp volume to minimum, connected power plug, no pickup, no speaker, first powered up on dim watt, no issue, then powered up regular, used my Fluke 115 set on millivolt, connected black lead to chassis, red lead to no 1 test pin, no reading ,tried to move the adjusting screw no change, put red lead on pin 1 of test and black on pin 2 of test ,no reading, tried to adjust R33 no change, set R33 back to minimum, set R25 to center, left volume at min, connected pick up, connected speakers, connected dim watt, turned box on got loud hum, inserted second board and with speaker disconnected and pickup not in, same issue no reading at test sockets. Where can i look for issue? pete PS does the amp only get the 25vac, i notice at the power pins its all i get, just confirming.
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