mcdoug3721
Super Member
I would guess that plug A is still installed. Seems likely that the short is on the main amp board if R301 is lifted and pre-main jumpers out. Hard to tell since there has been no confirmation as to the status of plug A.
Kenwood Ka6000
- Thread starter Dart07
- Start date
I think it was pulled earlier and we still had a bright bulb. Just wanted confirmation it it is still out.
mcdoug3721
Super Member
That leaves only the 24v to pin 3 on main board if plug pulled and R301 in place. Unlikely in Tuner. Like to see some voltages.
I will add a series of photos tomorrow, I don't have kena at hand today
plug "A", R301, C301 disconnected.
Attachments
Semanon
Super Member
Based on post 45, the jumper plug is removed. The positive wire from C301 is still connected. Corrected: This seems to be disconnected.
OP, do you have a multimeter to test continuity and voltages? The component tester is great for spot checks, but is not effective for the types of tests that are now required.
OP, do you have a multimeter to test continuity and voltages? The component tester is great for spot checks, but is not effective for the types of tests that are now required.
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Yes, I have a multimeter, c301 is connected with a wire with jumper A, unsolder it? I thought it had no effect...
Semanon
Super Member
In this photo, it seems as if th OP is cutting wires and leads to remove them. Normally they would be unsoldered. Use caution if you are cutting leads. It can result in loose bits of clipped leads when they are resoldered and sometimes the leads end up too short. See red circled area. may be seeing this wrong.
Semanon
Super Member
Yes I was wrong. I though it was still connected, not I see the end of it. Previous post corrected.
mcdoug3721
Super Member
It is not clear what the problem is here. Sounds like a perceived bright bulb (70W) when powered on DBT with no other known issues? The power supply seems to have been isolated. If so and there is a short, it must be in the power supply circuit. With R301 lifted the perceived problem is narrowed down to C301 short, the bridge rectifier diodes or the transformer.
@mcdoug3721 He did a DBT test with C301 disconnected (cut wire) and there was no problem. DBT dark as to be expected with a good bridge and no cap to charge.
It could be the diodes or the cap failing under voltage/load. At this time it is not clear. My gut says the cap, his tester shows a pretty high ESR, the uF value is close.
I don't trust those universal testers for larger value caps.
Yeah cutting wires is quick and easy but not recommended for several reasons.
You may not have enough lead length to put it back. (big red resistor)
It is harder to unsolder and remove the tail you cut off now that you cant get a hold of it to wiggle free.
It may leave wire bits as @mcdoug3721 said.
It could be the diodes or the cap failing under voltage/load. At this time it is not clear. My gut says the cap, his tester shows a pretty high ESR, the uF value is close.
I don't trust those universal testers for larger value caps.
Yeah cutting wires is quick and easy but not recommended for several reasons.
You may not have enough lead length to put it back. (big red resistor)
It is harder to unsolder and remove the tail you cut off now that you cant get a hold of it to wiggle free.
It may leave wire bits as @mcdoug3721 said.
mcdoug3721
Super Member
Yup C301 is the likely culprit. Possible diode yet unlikely given that they rarely go bad. I believe they were checked and appeared to be good? A new 4700uf cap will likely take care of things. As far as cutting wires, it is a extremely rare case where I would cut rather than desolder. Even wire wraps get unwrapped and rewrapped in most cases with some getting new wire. Depends on the unit.
Semanon
Super Member
Same. You are going to have to put an iron to it to clean it up and reattach the wire.
I did that, too, up to the point of buying a used wire wrap gun at a swap meet. But then it occurred to me that wire wrap was done for the benefit of the assembler (faster, one tool, no heat time, no cool time, etc.). It also made service more difficult than soldering. Now I resolder to the wire wrap post. Some may find it blasphemy, but it makes future service easier.
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Thank you for the tips, I try to cut as close as possible to save the wire so that I can solder. I exchange c301 and come back with information.
That will be OK for testing. Leave the plug out of the chassis jack for now.
there is progress, a light bulb flashed and dimmed...
I think the next step is to put the new cap in place of the old one and clean up the wiring. After that test again and if still OK then install the plug "A" for the amp power and test again. It certainly looks like C301 was the root of your problems.