Aiwa TPR-920 sound problems

[donahuest]

Hello. I have this Aiwa TPR-920 that has a volume problem. The volume plays really low. It will kick in at normal volume intermittently. It isn't scratchy at all just good volume and low volume no in between. I have it open and have a can of dioxin but am not sure where to begin squirting this stuff ro if it is even something that requires dioxin? So far I've only changed belts so this is new territory for me. I've attached a pic. Any help on where to start would be greatly appreciated. It sounds good when it does kick in so would love to get this bad boy back in action.

 

[Superduper]

It sounds like the contact feelers inside your volume control is either loose or dislodged. You may need a new one, or try to repair the one you have.

 

[donahuest]

Darn think that might be above my skill level. This thing looks like it was stored in some bad conditions so I’m not surprised

 

[MyOhMy]

Darn think that might be above my skill level. This thing looks like it was stored in some bad conditions so I’m not surprised

Please don't be put off by what you may consider your skill level to be as this sort of problem just may be a little easier to repair than you may think. It won't hurt to have a look and then decide, if you can't fix it at least you will have improved your knowledge level and expertise by a little just by looking. Even before this, try a search on the forum for 'feelers' like I just did - and brought up two pages of results which *may* help you.


Good luck!

 

[Superduper]

If wiggling or putting angular stress on the control improves the volume control situation, it pretty much confirms that the internal feelers aren’t making proper contact in the relaxed position like it should, ergo loose or detached or broken feelers.

 

[donahuest]

Thanks everyone for the encouragement and help, much appreciated. I guess I have nothing to loose as I didn’t pay much for it. I’m starting to really like opening these radios up, as frustrating as it can be.
When you guys refer to volume feelers are you talking about the left and right volume control knobs? The volume only kicked in a couple times at normal volume for about 5 min (sounded great and loud at 3), now the volume will adjust but even at 10 it sounds very low like a normal 1 or 2? I tried wiggling the volume and shot a bunch of deoxit in there but nothing.

 

[donahuest]

I’m wondering if the problem is with amplifier(s). Does anybody know how to start to troubleshoot to see if the amplifiers are OK?

 

[Superduper]

Might not even be the volume controls, could be the internal record bar, which is a long bar looking switch. All the signals go through this switch. Sometimes, when the connection is bad, cranking up the volume control could increase signal voltage enough to overcome the poor contacts sufficiently to restore volume for a bit. As a test, I suggest you put a tape in the deck and press record (might need to depress play at same time). Then stop. Do that for like 20 ~ 50 times. If you are getting improved results, it's virtually a sure sign that it needs cleaning. Squirting some deoxidizing solvent cleaner in there and working it will restore it. Or it could the the function switch. If you want more detailed information on how to do that, just search the archives. This question "cleaning the record bar" has been asked and answered countless times.

As for the amplifier, I doubt that it's the amp at all. The very fact that you are getting output, and loud output (albeit intermittently) is proof that the amp is capable of outputting a strong signal. The problem is that you need to feed the amp with a good signal to get a good signal out. Garbage in, Garbage out.

 

[donahuest]

Thanks a lot superdude 👍🏼. The record/ stop seems to have helped. It has kicked back in but still goes out periodically and I have to repeat process. I had it apart but didn’t know where to spray the deoxit. I’ll have to find out where the control bar is and spray it. Then add belts to cassette player while I’m at it.

Sulerduper rather. Thought that said superdude. This little aiwa sounds amazing. It was the dirtiest thing I ever seen though.

 

[Superduper]

If that little trick helps, even temporarily or slightly, then it's a sure sign that it's your likely culprit. Normally, I like to blow out really dirty boomboxes with compressed air. I take the open chassis out into the garage (or in driveway if very dirty), then take a shop air compressor with an air blow nozzle to clean out, does wonders and makes for a great starting point. Then for deoxit... see this thread for example of what it looks like.

BTW, you won't see that switch if you only have access to the backside since it's normally mounted on the component side. However, you can kinda figure out where it is simply by looking for the double long row of solder pads. It's probably the longest one if there are multiples of such switches. You'll find that there is a plastic protrusion on one side. You can likely push or pull on it and it will be spring loaded. I stand the board up so that the switch is vertical, then squirt a little deoxit on the top side so that the solvent can work it's way down as you work it. I think if you work it aggressively, you'll find marked improvement not only in gremlins but also in sound quality. Remember to soak up as much of excess solvent as you can afterwards, but stay away from any wound coils. Most are soft and can be deformed very easily. The mH value of those coils are adjustable by coil shape so deforming it could cause issues that you won't likely be able to fix since you'll never get it back like it was.

https://boomboxery.com/forum/index.php/topic/28289-record-switch-bar-example/?hl=%2Brecord+%2Bbar

 

[donahuest]

Nice info. Helps a lot. I’m going to open it up after I get home from doing some OT tomorrow. I took a picture last time I had it open.