Fixing a Mystery Ebay Legend
- Thread starter stragulus
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Oh Man, does that drag up bad memories!stragulus said:Crap! I dropped my test lead in the worst possible wayI heard the sound, and was instantly mortified:
IMAG3048 speaker punctured.jpg
I salvaged it by carefully applying black silicone caulk to the backside:
IMAG3068 speaker fixed.jpg
Still mad at myself, but it could be worse. Careful, careful, careful..
I was working on my car stereo, finishing the last bit, screwing in the last speaker and a slip of the screw driver right through the face of the speaker! 
I was ready to vomit! 
Your project is really making headway!
Looking forward to the completion!
The transistor is an important part of the regulator circuitry, typically which includes a current dropping resistor and Zener diode tethered to the transistor base. All 3 work hand in hand. Failure of either the transistor or diode will result in an failed regulator. If the resistor fails open, the regulated rail will have no output. If the resistor shorts, this will likely result in avalanche failure of the diode, full unregulated voltage at output, and possible transistor failure. If diode fails short, output will be low or none. An open diode will probably result in high voltage at regulated rail. Due to possible stress on the remaining appurtenant components after failure of any individual component, I like to replace the complete set of 3 together when rebuilding a regulator.
Failure of regulators are pretty common in electrical devices. Modern devices make use of IC regulators (i.e. LM780x series) which are fairly reliable if properly sized for the circuit protected. Some IC regulators are fixed voltage while some are adjustable. However,classic electronics such as '70's and '80's boomboxes usually incorporate the aforementioned resistor/transistor/zener-diode design. Having a good understanding of how these regulators work will help you when troubleshooting these types of circuitry problems.
Failure of regulators are pretty common in electrical devices. Modern devices make use of IC regulators (i.e. LM780x series) which are fairly reliable if properly sized for the circuit protected. Some IC regulators are fixed voltage while some are adjustable. However,classic electronics such as '70's and '80's boomboxes usually incorporate the aforementioned resistor/transistor/zener-diode design. Having a good understanding of how these regulators work will help you when troubleshooting these types of circuitry problems.
https://www.youtube.com/watch?v=0VkrUG3OrPcstragulus said:Woot! The transistor replacement brought the beast back to life!
And whow, is it loud! I got it to play around 11pm, so I didn't get to crank it past 10-15, but that was already quite impressive
IMAG3142.jpg
EXCELLENT WORK MAN!
What you started with and where you are now is just impressive!
My hat goes off to you and those that gave you input. Another C100 saved!
What you started with and where you are now is just impressive!
My hat goes off to you and those that gave you input. Another C100 saved!
Thanks for posting the problem, and the soulution!
I noticed it is not common to see here.
Good work!
I noticed it is not common to see here.
Good work!
Fully assembled, blasting with the others 
Both tape decks work now as well!
Still some issues to fix though. The tape door doesn't close properly because it doesn't hinge on the left side. The 'wide' stereo mode doesn't sound right to me, and it pops very loudly when selecting that mode when just turned on. All the rest is just cosmetic. Plus, I really should take it out to see how loud it really is, I don't dare to turn it up past 15 inside
Both tape decks work now as well!Still some issues to fix though. The tape door doesn't close properly because it doesn't hinge on the left side. The 'wide' stereo mode doesn't sound right to me, and it pops very loudly when selecting that mode when just turned on. All the rest is just cosmetic. Plus, I really should take it out to see how loud it really is, I don't dare to turn it up past 15 inside
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M90 prices are *insane*! Should someone wants to trade their (broken) M90 for my Helix in similar physical condition though, let me know!
I do have a Sanyo M9998 coming in and have really high hopes for that one, both for sound and build quality.
I do have a Sanyo M9998 coming in and have really high hopes for that one, both for sound and build quality.
Good read and congrats stragulus.
That box is lucky to have you as a friend.
This is what Boomboxery is all about.
That box is lucky to have you as a friend.
This is what Boomboxery is all about.
Way to stick to it and not give up. I know that feeling of cutting a speaker during repairs. It's no fun.
100%
Excellent thread!! So glad you got it working,great to find that you found that it was a resistor!!
I'm still looking for a Conion C100F.
Just excellent!!
I'm still looking for a Conion C100F.
Just excellent!!
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