Newbie just got a Promax J1 Super Jumbo, looking for parts and advice

[mattbran01]

As the title say, I'm new to boomboxes and just picked up a Promax J1 for what I think was a good deal. My initial plan was to grab something visually interesting, and hide a Bluetooth adapter and a modern rechargeable battery to have a cooler and more unique Bluetooth speaker. I saw this boombox had just been listed for $10, and they had a video of it somewhat working. I figured it would be a good learning opportunity at a minimum, so I offered them $15 if they would hold it for me until I could pick it up the next day (today). I've done some research tonight, and I'm not too sure I want to modify it much as these seem to be pretty desirable.

Either way, it didn't take long to determine that at least part of the issue is that a couple of the sliders on the EQ board were making the speakers clip in and out. After some disassembly, I found that one of the sliders (balance) had been previously broken and someone tried to glue it back together, but it had since fallen apart and there was glue all over the brushes. The slider on the main volume was the other problem child. That seemed to just be dislodged, but I was able to snap it back on. I haven't reassembled it yet to see if that fixed anything.

I know I'll have a bunch more questions going forward, but first thing first: where can I find these potentiometer sliders?

I also need a "b" cassette door cover and oned of the handle side bracket if anyone has a parts machine...

Looking forward to getting a lot of good insight from this group. I already learned a lot by reading before I joined.

-Matt

 

[floyd]

That's a great price !.
I can tell that the one slider is missing one of the feelers and the other ones are bent . it's going to affect the sound on some way . which slider is it a volume or eq band ?.

 

[mattbran01]

That's a great price !.
I can tell that the one slider is missing one of the feelers and the other ones are bent . it's going to affect the sound on some way . which slider is it a volume or eq band ?.

That particular broken one was for the balance. Does anyone selling replacement sliders? I'm not seeing a visual difference between the sliders themselves, some of the potentiometers just have different resistance ratings.

 

[mattbran01]

I've been tearing things down as far as I'm comfortable with, and taking a lot of pictures along the way. I was thinking about documenting my journey here, while asking some questions along the way. Should I just continue on with this thread, or just start a new one ( maybe in a different section)?

 

[Transistorized]

Should I just continue on with this thread, or just start a new one ( maybe in a different section)?

I would use this thread as it is in the tech section and is for repairs. BTW, $15 dollars is a steal.

 

[mattbran01]

I've got most of the plastic parts cleaned up and looking good. Now it's time to start cleaning the electronics. I've seen plenty of discussion about using contact cleaner (CRC QD) and Deoxit. I haven't seen much on which to use where, and which varieties to use for what for the Deoxit. Any guidance/ recommendations would be greatly appreciated.

I'm also nervous about doing much with the radio board. It's pretty dirty, but I'm scared to clean it and mess up the string drive system for the readout (sorry don't know the terminology). Is it a complicated process to reset that? Ideally I'd take the string off to get access to everything for cleaning, then reassemble when I'm done...

 

[floyd]

I've got most of the plastic parts cleaned up and looking good. Now it's time to start cleaning the electronics. I've seen plenty of discussion about using contact cleaner (CRC QD) and Deoxit. I haven't seen much on which to use where, and which varieties to use for what for the Deoxit. Any guidance/ recommendations would be greatly appreciated.

I'm also nervous about doing much with the radio board. It's pretty dirty, but I'm scared to clean it and mess up the string drive system for the readout (sorry don't know the terminology). Is it a complicated process to reset that? Ideally I'd take the string off to get access to everything for cleaning, then reassemble when I'm done...

Get a can off compressed air and a soft bristled paint brush . just clean it up the best you can without disturbing anything.

 

[mattbran01]

All of the potentiometers were very staticy (is that a word??). Should I at least hit those with some contact cleaner? Also the RCA connectors on the back are incredibly corroded. Deoxit on those? Thanks!

 

[Tinman]

staticy (is that a word??)

Google says no.
Staticky (or scratchy)

 

[floyd]

All of the potentiometers were very staticy (is that a word??). Should I at least hit those with some contact cleaner? Also the RCA connectors on the back are incredibly corroded. Deoxit on those? Thanks!

You can spray the potentiometer but I would stay away from the rca jacks with the cleaner. If you have some 1500 grit sandpaper just lightly go around the rca jacks to remove any corrosion.

 

[mattbran01]

Google says no.
Staticky (or scratch

Google says no.
Staticky (or scratchy)

Haha, I had the "k" in there for a second, but that didn't look right either.

 

[mattbran01]

Quick update. I finally found wipers/sliders for the potentiometers!! After several failed attempts of using Google lense, I finally took a pic at the correct angle to get a match. I ended up getting (8) full potentiometer assemblies for $12 including shipping from Ali Express. The potentiometers weren't the correct resistance, but since I only needed the wipers, I didn't care. I'm sure if I searched long enough I couldn't find an exact match. Now I,m waiting to get 99% IPA from Amazon because I can't find anything above 91% locally without buying a gallon.

A quick question: all of the push buttons and the chrome slider handles were glued on with some sort of stretchy glue. Should I be gluing these back on, or just rely on friction fit?

 

[Tinman]

Quick update. I finally found wipers/sliders for the potentiometers!! After several failed attempts of using Google lense, I finally took a pic at the correct angle to get a match. I ended up getting (8) full potentiometer assemblies for $12 including shipping from Ali Express. The potentiometers weren't the correct resistance, but since I only needed the wipers, I didn't care. I'm sure if I searched long enough I couldn't find an exact match. Now I,m waiting to get 99% IPA from Amazon because I can't find anything above 91% locally without buying a gallon.

A quick question: all of the push buttons and the chrome slider handles were glued on with some sort of stretchy glue. Should I be gluing these back on, or just rely on friction fit?

Try them and see if they feel loose.
If they don't, then you're good.
If they are, you could try a very small piece of masking tape on the tip of the plastic piece then push the chrome part on.
Don't over do it, too much and they get too hard to slide on or off.
The tape acts like a thin shim.
If you rather use glue, use one that doesn't harden and only a very very small amount.
You want to be able to remove them without damage if needed.