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PostPosted: 13 May 2016, 21:59 
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Joined: 13 May 2016, 21:30
Posts: 3
I have a Model 88 that sounds fantastic when you first turn it on, but after a few minutes it goes completely silent, but you can get it back by adjusting the volume up or down. Volume controls are digital, so it's not something simple like a dirty volume control pot. I do not have a schematic nor is there one available to my knowledge. My first thought is a possible bad control pushbutton or poor connection (cold solder joint etc) I can't see a problem but just curious if anyone thinks it might be worth the trouble to replace these or does this sound like and IC problem?

I don't have a scope so I can't follow the audio, I'm hoping to just try replacing a few parts, visual search for bad connections. Could it be a grounding problem, or a speaker problem? Just hoping for any feedback, these are incredible little radios when working properly, but nobody repairs them so you kind of have to give it a shot yourself.


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PostPosted: 15 May 2016, 08:30 
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Joined: 13 May 2016, 21:30
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Indy_Mike wrote:
I have a Model 88 that sounds fantastic when you first turn it on, but after a few minutes it goes completely silent, but you can get it back by adjusting the volume up or down. Volume controls are digital, so it's not something simple like a dirty volume control pot. I do not have a schematic nor is there one available to my knowledge. My first thought is a possible bad control pushbutton or poor connection (cold solder joint etc) I can't see a problem but just curious if anyone thinks it might be worth the trouble to replace these or does this sound like and IC problem?

I don't have a scope so I can't follow the audio, I'm hoping to just try replacing a few parts, visual search for bad connections. Could it be a grounding problem, or a speaker problem? Just hoping for any feedback, these are incredible little radios when working properly, but nobody repairs them so you kind of have to give it a shot yourself.


OK...since I posted this I have had a chance to disassemble the radio. Mainly I was just inspecting it to see if I could find any obvious signs of concern, I found nothing suspicious, i.e. hotspots, loose connections, water damage etc. Also, there are no pushbuttons on the control board like I expected, just graphite contact points pushing against the board to activate the switch. Also, I spent a little more time after re-assembly trying to determine the exact symptoms:

1) when you turn the radio on it goes to volume level 3 and it plays the radio. The radio has three audio settings (stereo, wide, and mono) in stereo, only the left speaker and sub-woofer is working, in wide all 3 speakers seem to be working fine, and in mono none of the speakers work.

2) If you do nothing and let it play, after about 2 minutes the audio will slowly fade out, the only way to get it back is to raise and lower the volume back to volume level 3 or 2, or if you go higher it will sometimes come back on at say volume level 6 but the volume is no louder, so I'm not sure the volume control is even working.

3) When you push the volume up or down buttons there is a pop each time.

4) One last weird thing, it has a AUX input, I hooked my IPod into it and it behaves the same way as the radio (audio fading out, bringing it back with volume level change) but when I went higher in the volume level, say 11 or higher, the radio could be heard bleeding through.

I appreciate anyone that has ever experienced any of these problems with audio equipment to comment. I realize my explanations might be a bit confusing. This might be a lost cause but I am certainly willing to replace some components on the board level to try to repair it since no parts are available. My best bet might be to just get another non working unit and swap some parts?


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PostPosted: 16 May 2016, 13:43 
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Joined: 09 Oct 2012, 19:43
Posts: 284
Location: Vancouver Canada
With that machine i would say just keep going with what you are doing. Probably it is the control ic's but you never know. It will depend on the level of integration inside the box, as to how far you can diagnose. The more modules that are in it, means the more cir's that can be isolated and checked individually. Don't finger the black dot in the sw-buttons though. It rubs the surface carbon off and introduces oils that will be placed on the exposed PCB tracks to later corrode the copper.
You may try contacting the warranty repair places for sch's etc. They often will give up a copy if the units are far off warranty and or no longer in production. Lots of luck.


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PostPosted: 16 May 2016, 15:19 
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Joined: 08 Aug 2009, 03:11
Posts: 2195
Location: Chilliwack, BC
Hi,

Check the solder joints and connectors on those, especially the ribbon leading to the keypad.

There is possibly overheating damage done to the chips and capacitors (recap it if you see the cap-wrap pulling back off the tops) becaue people see a little radio and try and play boom-box with it. The biggest complaint is they shut down after a while, but that's usually because they have it up to "200" and it's going into thermal protection :hot:

I am a Cambridge warranty depot and even we don't have a schematic for it.... HQ just orders it destroyed and sends the customer another. They're too cheap.

Cheers!

_________________
-= Gregg =-
* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
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PostPosted: 16 May 2016, 15:32 
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Joined: 13 May 2016, 21:30
Posts: 3
Very much appreciate both of your comments. I will probably go ahead and touch up some of the solder joints as a few have lost their shine...might be worth a shot. Replacing the caps might also be worth it. I'm not even opposed to replacing the IC on the control board if I can find a replacement.

These radios might be inexpensive compared to high end audio equipment, but I think the quality of their sound is pretty amazing for their size. I have a working one that sounds awesome, my wife uses it daily, and if I tried to use it (swap boards) to troubleshoot this one, she would probably have my legs broken! LOL!

Thanks again....I am also still looking for another broken one on Ebay and elsewhere. Thanks again!


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