Hello /diy/ers.
I have an amplifier that i found and it's in pretty good condition. I changed some elements and made it work (sound-wise). The problem is that lights are not working. Voltage across the board for lights gives 0 volts. Maybe it transformer fault or maybe something on the board isn't right. Can you suggest me how can i check if it's the transformer or something else.
ALSO, I would like to ask if there is some way i can make lighting out of LED, using a second power source (12 volt converter or something else) and connecting LED, resistors to the button to get same effect like those lamps had
Thank you
>>908313
I forgot to tell.
It's sanyo dcx 8000k from 1970s
I think that schematics for light are bottom right after gretz compound
Sorry if some words are weird, but english is not my native language and I'm trying
>>908315
this is the lighting board
>>908316
I have never encountered this before, so could someone tell me if these are for light slots, or are they 5A fuse slots
Did you check the fuse?
>>908319
fuses are all new and changed. Everything works but light. i can play radio, and sound is coming out amplified.
>>908317
http://www.parts-express.com/6-volt-250ma-original-style-fuse-type-lamp-for-marantz-sansui-kenwood-yamaha-sony-and-o--070-118
Check aliexpress or something for cheap LED versions.
I didn't know this even exists. Thank you so much, this removes so much thinkering.
But i still have to fix the board for it to work
board should be operating at 7.2V
>>908313
>Voltage across the board for lights gives 0 volts.
If you are using a digital meter switched to DC volts on a AC circuit this is normal. Change it to AC then measure again.
>>908324
I measured both. I got even desperate to switch between all possible numbers. and measured with another voltmeter just in case.
in picture 3, you can see red lamplight sticking out of amplifier. It's not working when all fuses are put in
>>908325
Check if the resistors associated with the lamps and the voltage from the lamp winding on the transformer. You want the meter on AC volts. The 50 volt range is reasonable for a start if its a non auto ranger.
>>908323
That board would have seen thousands and thousands of heat/cool cycles, over time this can cause the solder joints to fracture from constant thermal expansion and contraction. It is likely there are fractured solder joints all over it, which may be breaking the circuit. Rework all the solder joints on the board and see how you go. Be very careful to apply only as much heat as you need, and get the joints reworked as fast as you can. Tracks on boards that old need no excuse to lift away from the PCB, especially in a board that has seen as much heat as that one.
I also notice that all the lamps seem to be supplied from one point, the circled coil of the mains transformer. Get your meter out and verify this winding is delivering power, if so get your meter and follow the wires/tracks till the voltage disappears. There will be your problem.
That's a beautiful old amp man, you're doing gods work restoring it. Good luck.
>>908328
thank you so much. firstly i fell in love when i have seen wooden construction. then the sound .
Why do i have to work as fast as I can?
can you explain maybe, because im interested
>>908330
Well, the board and the copper, being different materials, expand and contract under heating at different rates. This is not problem in low temperature environments, but for a PCB that is mounted above the globes this will be a big issue. Over time the difference in expansion and contraction rates causes the copper (or whatever metal the tracks are made of) to separate from the board. Another factor is the adhesive they use to fix the copper to the board failing over time, leading to the same outcome.
Pic related is a perfect example, a power supply board from a 50's era mainframe terminal. Over the years the constant heat and cool cycling caused by those chunky, high watt resistors has caused the tracks to lift away from the PCB. Circled is an example of a fractured solder joint that I referred to in my other post. This board is toast, and I plan to etch my own replacement board to get the device working again.
>>908332
Looks like the transformers leads come out underneath the chassis. Pop the base plate off and take a photo of the underside of the unit and i'll see what I can find.
>>908336
here it is
although i will have to unscrew each board separately since those connections are on the other side i believe
>>908336
> leaving an entire paragraph out of my response.
>Another factor is the adhesive they use to fix the copper to the board failing over time, leading to the same outcome.
To finish this thought, any mechanical action, be it the component leg moving or the iron tip can cause the pad to lift. The heat from the tip can also cause a "just hanging in there" pad or track to lift off the PCB, making resoldering the component to the pad a bit of a bitch. The less time you can spend hanging around with your iron tip, the better, especially on 20+ year old boards.
>>908337
Yewww, what a rats nest. Gimmie a minute or two to dig..
>>908338
Hmm, I think someone has been hacking around in this thing OP. This unit should have two panel mounted fuses (one per channel) for overload protection and a mains fuse. Three in total according to the schematic. In your unit, I see at least 5. I say at least, because I would not expect the mains fuse to be located so haphazardly on the bottom of the transformer like that, the mains fuse may be on a PCB somewhere (if anywhere, the power supply board, mounted immediately right of the transformer with the blue capacitors) which means those three fuses have been added because reasons. What those reasons are is anyone's guess.
The red wires I have highlighted with blue lines do not appear to be in a factory position either, wires are never passed through holes in metal without a grommet (to stop vibration wearing through the insulation, resulting in a short to chassis) nor are they strung as tightly as the wire on the right is. They would be bundled in with the rest if they were factory original. The brown wire in the inset image also appears to be a poor hack job done after it was built. Not sure whats gone on in this poor stereos history, but it appears to have been rough.
I was going to suggest that your lights will be powered by the only wires that DO NOT terminate on the power supply board (according to the schematic) but considering the works done I'm not sure what is going where in there. Might be time to flex that EE muscle and learn to circuit trace, or lug it to your next class and see if someone there can help you trace it out. Not much I can do from this point without it on a bench if front of me unfortunately.
Your English is better than a lot of native speakers I know by the way. Stress less.
>>908342
..and forgot to mention, the lamps are switched via the "Function" rotary switch on the front panel. S(witch)10 and S11 would refer to individual decks of that switch, S6, 7, 8 and 9 also appear to be decks on that rotary. Each switch "layer" in a rotary switch is referred to as a "deck" where I am, terminology may be different where you are, but to be clear, pic related has three decks (layers of switches), your function switch has 6 from what I can see in the bottom right of >>908337
Find which deck the lamp board connects to, and see if you can work your way back to the mains transformer from there.
>>908342
yes, those soldering remains on fuse slot are from previous owner which i do not know who he is... He also hacked (with a knife or whatever) through metal plating to get to lamps so he can switch them.
Yes it's a bit messy, but i believe it's awesome considered it was found in an old factory that was closed in like 15-20. I'm big audiophile, but i like to have it look nice and have lights. Thank you for all your responses, I will try to look and follow >>908342 those wires you mentioned.
also, any simple way to see if transformer channels?/input-output paths are working properly.
>>908363
That guy sounds like a barbarian.
>transformer channels
You mean the transformers secondary coils? Sure, Grab a multimeter and test like this >>908326 guy suggested. Look closely at the schematic and you'll see there are voltage reference points (including for the AC output of the transformer, 36V). Again, expect at least 6V on the secondary that powers the lamps, likely more. Gotta get them lamps working, half the appeal of these old units is the warm glow of an actual filament as opposed to a LED. Comfy as fuck.
> input-output paths are working properly.
If the amp works but you want to check that it is within electrical specifications, you'll need a signal generator and oscilloscope. Select the input you want to test, inject a clean signal via the appropriate RCA connector on the back, and trace the signal through each audio stage to make sure no distortion, hum or other problems are introduced, You'd be very lucky to find a service manual (and the calibration parameters within it) to perform a complete service, but the scope will at least show you if something is introducing noise, allowing you to dig around in that circuit section for culprits. Get some contact cleaner and hit the potentiometers and rotary switches, as well as every button you can find. Be prepared to replace a lot of electrolytic capacitors as well, some of the ones in there are bound to be pretty close to dried out, and these WILL introduce noise when they go bad.
If you have a dead or faulty channel, follow the advice I dropped in another thread, >>906874, and work your way from the output back to the input. Get used to the concept of block diagrams and signal chains, they will be the easiest way to get an overview of what your device has, and where given problems are likely to be.
>>908369
i already used contact cleaner on them just in case, there wasn't any distortion but there was cracking noise when i would turn volume up and down etc. capacitors are still functioning, but i have bunch of spare ones laying around if i need them. after i plugged it in the first time there wasn't white smoke coming out haha.
as for the broken channel, channel phono 1 or 2 didn't work so i just thought to not use it at all, as I'm mostly using aux. but since you mentioned it I will try to repair it also and try to get it as close to mint condition i can
>>908313
Please tell me that you have already measured the resistance of the bulbs and that they are not open. Did you actually test the bulbs outside of the circuit, ie with a second power supply?
>>908509
no i did not. They're factory so they should be fine?
>They're factory so they should be fine?
ha! bulbs are not LEDs, they have a pretty short lifespan. replacement flashlight bulbs, for example, from Radio Shack, have an average lifetime of 200 hours. in stereos, they're gonna run the bulbs at 50% power so they last longer, but it's still quite a short life. i would expect every bulb in that receiver to be dead unless they've been replaced at some point.
>>908828
light bulbs are dead, but nevertheless, I should get some voltage across that power circuit.
Also I can see that it hasn't been used too much, because all resistors, capacitors and transistors are working fine, and look as they should
