Re: Pioneer sx-727 radio dead

On May 11, 10:13 pm, "Mark D. Zacharias" <mzachar...@xxxxxxxxxxxx>
wrote:
<tx7...@xxxxxxxxx> wrote in message

news:89bc8f04-d26f-4237-8b8a-3f1495b191b6@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On May 11, 9:07 am, "Mark D. Zacharias" <mzachar...@xxxxxxxxxxxx>
wrote:





<tx7...@xxxxxxxxx> wrote in message

news:b2fdab22-8f8c-4c93-a720-d79cc0fe3bff@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On May 3, 5:19 pm, "Mark D. Zacharias" <mzachar...@xxxxxxxxxxxx>
wrote:

Hi ,

<SNIP>

I decided to lift the board and look at the solder for the device

sanyo 313e.
Before I could do anything the V shaped metal (heatsink?) attached >to
the
device just fell off. The plastic screw holding it had just cracked >in
half.
There also is a thin piece of plastic between the device and the
heatsink.
I'm assuming that they do want the device to touch the metal.
I could not find a another plastic screw, so I use a metal one with
<an
insulating washer. I hope that is ok. Why does the device need to >be
insulated from the metal heatsink. Is it strictly pecautionary, in
case
the heatsink comes in contact with something else. Would it be ok
to put some cpu grease between the device and the plastic >insulator?
Anyway after all this the solder looked ok, so I did not resolder.
I wonder if my problem all along was that the heatsink
was just hanging on by a thread.

Anyway it seems to work ok. I'll run it for a while with the case>open

as a precaution.

Thanks

If the solder is really OK, which I doubt. Then the transistor is failing.
On this TO-220 case transistor this most commonly happens from a
base-emitter junction opening up internally.

If you were to look very closely at the solder connections ( I recommend a
magnifying glass) I believe you will see the ring-cracks around the
transistor leads.

In this particular case the heat sink has no other electrical connection,
but you are still going to need another screw and nut. Another mica
insulator and some silicon grease would be good, although as I say, in
this
case I think you could dispense with the mica.

Alternatively you could use a newer style TO-220PL plastic case transistor
such as a 2SC4793 which requires no insulator.

It's unfortunate in a way that your skills and experience don't seem to
quite be up to the task. I don't say that as a put-down, but this whole
thing should have been over long ago.

If you decide to replace the transistor, you'll need a source for the
part,
and most suppliers have 15.00 to 20.00 minimum orders.

You might consider OEQuotefix to fix your problem with Outlook Express
making messy looking posts. It's a free download.

Mark Z.- Hide quoted text -

- Show quoted text -

No need to be nasty.
The solder looked ok to me.
The board is very old,  so the plan is to proceed cautiously.
I have attached the device properly to the heatsink.
If the problem recurrs, I will reheat the solder joints.
If that does not solve the problem then I will  replace the device.
I'm assuming that a 2sd613 will be an adequate replacement, correct?

*****************************
A 2SD 613 would be fine.

I'm not sure why the > marks aren't showing in the quoted sections, I had to
add them manually last time.

I don't feel I was being nasty before, even said so:

I don't say that as a put-down, but this whole
thing should have been over long ago.

I was watching as several other responders were telling you to replace the
transistor and a lot of back-and-forth when as I say this coulda / shoulda
been over with long ago.

mz- Hide quoted text -

- Show quoted text -

OK thanks sounds good.
One more question.
In the process of lifting the board to examine underneath,
the plastic tabs that hold the board in place are very brittle.
One broke and the others half broke off. Can I pull these out
from the side that the power supply board is on?
I'm thinking that mayb I can replace these with some
computer mainboard ones that I have lying around?

Thanks
.

Relevant Pages

  • Re: Pioneer sx-727 radio dead
    ... Before I could do anything the V shaped metal (heatsink?) attached>to ... Anyway after all this the solder looked ok, ... Then the transistor is failing. ... insulator and some silicon grease would be good, although as I say, in this ...
    (sci.electronics.repair)
  • Re: Pioneer sx-727 radio dead
    ... It worked flawlessly for about 3 days, then spontaneouslt theradio ... by looking for cold/broken solder connections under a magnifying. ... Before I could do anything the V shaped metal (heatsink?) attached to ... I could not find a another plastic screw, so I use a metal one with ...
    (sci.electronics.repair)
  • Re: Pioneer sx-727 radio dead
    ... Before I could do anything the V shaped metal (heatsink?) attached>to ... The plastic screw holding it had just cracked>in ... Anyway after all this the solder looked ok, ... transistor leads. ...
    (sci.electronics.repair)
  • Re: Pioneer sx-727 radio dead
    ... Before I could do anything the V shaped metal (heatsink?) attached>to ... The plastic screw holding it had just cracked>in ... Anyway after all this the solder looked ok, ... Then the transistor is failing. ...
    (sci.electronics.repair)
  • Re: Pioneer sx-727 radio dead
    ... Before I could do anything the V shaped metal (heatsink?) attached>to ... Anyway after all this  the solder looked ok, ... Then the transistor is failing. ... insulator and some silicon grease would be good, although as I say, in this ...
    (sci.electronics.repair)
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