6 pin CD box needing repaired

[Want to be]

I removed the 8 screws. (4 OS and 4 IS) and the PCB won't let go. Do i need to clip a few wires or solder suck them. What a pain in the ass design. I thought i would ask before de-soldering.

Also I've read the 2N3055 power transistor is the most common part needing replaced.

thanks for any help.

jpc

[Joe Bob]

Ingo, 3.6@cox.net

[Want to be]

im sorry Joe bob, ugh?

[James Brown]

yes you have to de solder the 6 leads to take it apart

[Want to be]

no fun. thanks very much. is the transistor commonly needing repaired on the next layer of pcb.
?
I did not see the common transistor mentioned above?

[Want to be]

NLA? I dont have a scope but I do have the ability to test it via porsche

[T77911S]

its usually the capacitor mounted under the PCB. you can test it with a MM once you remove the back.

the wires are a pain to unsolder. they are inserted in those clips then they are squeezed together. then the other problem is the clips or posts will come unsoldered. although once the PCB is removed, you can resolder them after cleaning them up. then its just a matter of wiring it back up.

a good test is if it whines, thats good. then its usually the cap. if it does not make any noise, its in the oscillator section.

[Bob Ashlock]

Good advice ... they generally are repairable, but you do need to do major surgery (removal of numerous wires) just to get the board out so you can get at the critical power components. Take a photo before disassembly so you can keep track of everything and where each wire goes. I don't really think Bosch intended to service these things, as the labor to rework them likely exceeded the manufacturing cost. Anyway, the power transistor may break-down under load, or fail completely killing the oscillator/converter. The large storage capacitor often appears good with an ohmmeter, but will breakdown when the voltage across it increases.

I also regularly repair these things as a service to Porsche enthusiasts like myself.

Bob - Home

[Want to be]

Do I need to be concerned about capacitors or other parts holding charge? In regards theengineering of it being repairable. I ge it. Fifteen years ago I helped produce radios for several manf and it was a nightmare of pcb boards. Though it was easier to service than this thing. Lol
Many thanks on the help. Does frys or radio shack have the transistors?

[Bob Ashlock]

Since you are bound and determined to do it yourself .... ha ha ... just like I would be ... here is some info:

I have not seen anything in these units hold a charge very long. But I always play it safe and make sure I short the big storage cap to ground "just in case".

The main power transistor (2N3055HV) used by Bosch was a specially "selected" part that was rated for 100V breakdown voltage. In other words, not just any 2N3055 will work as they are only rated for 60V.

The main storage capacitor can be replaced with a high-quality high-voltage polypropylene pulse capacitor. Do not attempt to use a standard aluminum electrolytic cap as they cannot take the heat and current surges.

These parts are not available at your local Fry's or Radio Shack. Contact me for more info about obtaining the correct parts: bob@AshlockTech.com

[HawgRyder]

The best replacement I can come up with is a 2N6547 ... about $5.08 from Digi-Key.
It's rated at 400V / 15A.
Bob

[Bob Ashlock]

That looks like a good choice. You can also use the 2N3773. It's rated at 140V and 16A and has good gain. It's available at Mouser for $3.51

[Mark at Pelican Parts]

Pelican Parts offers CD box repair! Give us a call at 888.280.7799 7am - 5pm PST and we'll take care of your repair needs.

Mark/Pelican Parts