I'd posted earlier about a hum problem in a Nakamichi CR-4A cassette
deck.
Unfortunately it wasn't loose ground screws.
I found a couple of burnt resistors on the Power Supply PCB mounted on
the rear chassis panel
The part# for the board is 0B60525
the resistors in question are listed as R405 and R403, they'r to badly
burnt to tell what value they are.
Does anyone here have the schematics on this deck?
If so would appreciate it if you could post the values.
If anyone knows what value resistors wouldbe safe as a replacement I'd
appreciate that inof also.

"none" wrote in message
...
| I'd posted earlier about a hum problem in a Nakamichi CR-4A cassette
| deck.
| Unfortunately it wasn't loose ground screws.
| I found a couple of burnt resistors on the Power Supply PCB mounted on
| the rear chassis panel
| The part# for the board is 0B60525
| the resistors in question are listed as R405 and R403, they'r to badly
| burnt to tell what value they are.

That would make me guess that the main filters might be bad.

N

They are both 1000ohms, and being burnt almost certainly means that C406 & C407 went bad first,
both being 100uf/16v. These are voltage reference filters in two separate regulator circuits,
and would account for the noise. Gotta wonder if this is a case of a minor power line surge,
as I've never seen this failure pattern on a CR series deck before.

--
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"none" wrote in message ...
I'd posted earlier about a hum problem in a Nakamichi CR-4A cassette
deck.
Unfortunately it wasn't loose ground screws.
I found a couple of burnt resistors on the Power Supply PCB mounted on
the rear chassis panel
The part# for the board is 0B60525
the resistors in question are listed as R405 and R403, they'r to badly
burnt to tell what value they are.
Does anyone here have the schematics on this deck?
If so would appreciate it if you could post the values.
If anyone knows what value resistors wouldbe safe as a replacement I'd
appreciate that inof also.

On Mon, 27 Dec 2004 22:04:57 -0700, "Stephen Sank"
wrote:

They are both 1000ohms, and being burnt almost certainly means that C406 & C407 went bad first,
both being 100uf/16v. These are voltage reference filters in two separate regulator circuits,
and would account for the noise. Gotta wonder if this is a case of a minor power line surge,
as I've never seen this failure pattern on a CR series deck before.


Thanks for the info.
It's likely a case of dirty power. The power in out locale is
notorious for huge surges.(I've seen it go as high as 150 off the box
in my house. We suffered a burned out appliance or two when we first
moved in and have since invested in an voltage stabilizer box on the
mains side of my breaker box.)
The deck in question belonged to my neighbor down the street, who sits
just off the transformer for our block. That particular transformer
blows every 3 years or so like clockwork, usually during heavy summer
loads.
Thanks again, I'll replace all the resistors and see if it stays
fixed.

On Tue, 28 Dec 2004 04:22:00 GMT, "NSM" wrote:


"none" wrote in message
.. .
| I'd posted earlier about a hum problem in a Nakamichi CR-4A cassette
| deck.
| Unfortunately it wasn't loose ground screws.
| I found a couple of burnt resistors on the Power Supply PCB mounted on
| the rear chassis panel
| The part# for the board is 0B60525
| the resistors in question are listed as R405 and R403, they'r to badly
| burnt to tell what value they are.

That would make me guess that the main filters might be bad.

N

Correct, The PS pcb has staged noise filters to keep out power
transformer and line noise.
Which, with half the resistors being fried would explain the low level
buzz.