Need help please with some problems in a Conion C100F.

[CONION C100F]

Hi, I need some help with some problems with a Conion C100F please, if anyone out there has any ideas/solutions?
1. Constant humming noise/sound when turned on.
2. When I opened it up I found that someone already has been in there and changed the transformer and wiring on the circuit board PCB 8, and added a capacitor.
The tuner dial light doesn't work because it's been cut off from the circuit and the bulb is blown aswell and the switch for the 120/240V doesn't work either.
3. The mono/stereo/stereo wide switch is faulty/playing up, it doesn't work on stereo wide mode and is very noisy when switching between them.
I've taken out all the circuit boards and cleaned all the switches and pots etc but still not much good.
Is there anywhere else I can connect the tuner dial light up to?
4. I found a large blue capacitor connected to the blue and white wires coming from the power/alarm switches circuit board PCB 20 to reduce humming noise but 1 end broke off and I connected another 1.
Anyone out there has any ideas/solutions for all this please?
Some photos to show details of the above.
Thanks in advance.

 

[caution]

There's a really big cap on the amp board, I've had to replace that in the past to solve constant buzzing issues, so you shouild pull that off and check it. It ties directly to 15V.

The dial light uses a special winding in the transformer that puts out 7V AC. Since you no longer have the original transformer, rig something up with another bulb or better yet some LEDs, and tie into 15v. I've done this on at least four of these and always swap out the bulb in that metal cage with some white LEDs and a regulator.

The stereo mode switch seems to suffer from contamination buildup more than the other switches, it's always a royal pain to get working with just spray, Not sure if it's from arcing during switching but it seems to develop a coating of carbon on the contacts. I've always had to pull the switch and disassemble it for a thorough cleaning before it goes back to normal.

 

[CONION C100F]

Hi, thanks for your reply.
I'm not much good with electronics but I try my best to learn about it so I can do most things myself.
That big black cap is a new 1 I replaced because it had an even bigger blue 1 there when I opened the back up.
Without any caps connected there, the humming noise is much worse and you can't really hear anything else without it.
With the tuner dial light, you'll have to show me what parts to use and how to connect all that up because I've never had to do anything like that.
And the stereo switch, well I guess I'll try some more cleaning with that and see if it comes good or not.
Also the spare tape draw on the bottom is missing, I'll see if I can make something for that.
Thanks again for your input, hope to hear from you soon

 

[Superduper]

On the factory C100 transformer, it had a dedicated extra winding that allowed the dial lamp to be illuminated when powered on AC. But modern replacements don't have that extra (probably specially wound) winding to power the dial lamp so unless you supplement the circuit by adding an additional small transformer, that feature is lost. The same is true with the Sanyo M9998 and I had to stuff a small transformer in there to restore that feature on a blown power supply for someone.

That turquoise axial cap is only rated at 16V. Not sure where that went, but it definitely is rated too low in voltage if tied to the rails. I can't make heads or tails of what's what based on the photos, and none of the caps are mounted on PCB, they're all just tied and floating in the air secured with zip ties. It's unclear if these are contributing by being susceptible to noise. Also, the power PCB looks like it used to have a transformer mounted directly on it. Using an alternate transformer to replace a blown one is not uncommon but keep in mind that the orientation of the transformer mounting can have implications on hum. If it's not mounted like how the factory had it, that's worth looking into. Also, there seems to be something funky going on with the rectifier diodes. Not sure if it's supposed to be like that, maybe caution can chime in. But it looks like they are supposed to be mounted differently. On the board, there is layout for 4 diodes which suggests that it's a bridge rectifier. On bridge rectifiers, diode leads are tied together in a square shape with 2 of the tie points going to AC and the other 2 being rectified DC. With the 2 diode leads tied together with no circuitry connected to the tie point, I don't see what's happening there, not to mention that the 4 ceramic caps which runs across the diodes can't be doing it's job, at least 2 of them anyways.

See this image for representation of a typical bridge rectifier. Note how each diode lead tie is connected to circuitry. Yours have 2 tie points floating not connected to anything. Overall, there's some really funky mods going on and honestly, seeing the mess here, I don't think this is going to be an easy fix by any means. There's just to many unknowns, and where there's smoke, there's fire. In other words, there's probably more mods than meet the eye that one might never be able to find and correct.

 

[caution]

Hi, thanks for your reply.
I'm not much good with electronics but I try my best to learn about it so I can do most things myself.
That big black cap is a new 1 I replaced because it had an even bigger blue 1 there when I opened the back up.
Without any caps connected there, the humming noise is much worse and you can't really hear anything else without it.
With the tuner dial light, you'll have to show me what parts to use and how to connect all that up because I've never had to do anything like that.
And the stereo switch, well I guess I'll try some more cleaning with that and see if it comes good or not.
Also the spare tape draw on the bottom is missing, I'll see if I can make something for that.
Thanks again for your input, hope to hear from you soon

It would be difficult to explain the LED setup because each one I did was a little different. Bottom line, you want to add 1 to 3 LEDs and connect them either in series or in parallel to the 15V rail. How you accomplish this - resistor divider, 6V/9V/12V regulator, etc. is entirely up to you. If this is too much, you could always just use a bulb that supports 15V.

 

[CONION C100F]

Ok thanks for your reply.
I'll have to figure it out somehow.