Buzz on Audio Pot Travel Denon PMA-520

[[email protected]]

I'm getting a barely discernable "buzz" between the 10 and 12 o'clock
positions on the volume pot of my Denon PMA-520 integrated amp. I
cleaned with Deoxit, no change. Does this indicate there is a bad
spot on the pot, or could it be something else? The pot has the
following written on it:

2110524005-100K??x2

The ?? are some weird character, might be a japanese letter or
something. The pot is made in japan.

 

[Arfa Daily]

I'm getting a barely discernable "buzz" between the 10 and 12 o'clock
positions on the volume pot of my Denon PMA-520 integrated amp. I
cleaned with Deoxit, no change. Does this indicate there is a bad
spot on the pot, or could it be something else? The pot has the
following written on it:

2110524005-100K??x2

The ?? are some weird character, might be a japanese letter or
something. The pot is made in japan.

One channel, or both ? All functions ? Recently started or always been like
it ? I would suggest that the first bunch of numbers are just a
manufacturer's part or catalogue number. Might incorporate a date code -
week 40 2005 maybe ? 100k is the value in ohms, as in 100,000. The unknown
characters which follow, may well indicate the taper, which in English, is
usually "A" or "B" for linear or log (can't remember off the top of my head
which way round, without looking). The "x2" I would think is "times two"
indicating that it is a dual pot, as you would expect with a stereo
amplifier.

As far as whether the symptoms indicate a bad spot, you need to answer my
first questions, but first guess, I would have said not, as I don't think I
can ever remember a 'traditional' bad spot causing what you seem to be
observing.

Arfa

 

[N Cook]

I'm getting a barely discernable "buzz" between the 10 and 12 o'clock
positions on the volume pot of my Denon PMA-520 integrated amp. I
cleaned with Deoxit, no change. Does this indicate there is a bad
spot on the pot, or could it be something else? The pot has the
following written on it:

2110524005-100K??x2

The ?? are some weird character, might be a japanese letter or
something. The pot is made in japan.

A simple way to confirm/eliminate is temporarily solder say a 50K between
wiper and one end , for each pot, and see if the problem spot moves.

Rang a bell symptomwise and this repair brief off my files, off URL below

Cambridge Audiolab 8000C preamp 1994
Both channels function ok but with no or low signal there is a low level
mains hum. Hum for only about a third of full range of vol
control,when present it is constant volume regardless of vol setting. When
hum is present the
setting of the tone controls makes no difference to the amplitude of hum.
The mains transformer was 30v-0-30v with 120 deg C thermal fuse. This unit
is double insulated with phono connector returns commoned but not to ground.
With the earth point disconnected there was significant voltage on the
chassis.
138 V ac one of the secondaries to ground and about 110V ac chassis to
ground.
With 3.3M connected between chassis and ground there
was 60V ac so 20 microamp of leakage between primary and secondary.
Although 500 V megger insulation test showed >200M between primary and
secondary.
On changing the transformer noticed one of the chassis screws was far too
long
in the area of the mains switch. With time the end of the screw had pushed
into
and deformed the insulation around the mains line at that position. It had
not
punctured through but is obviously undesirable so replaced with a screw only
1/3 the length
of the original. So SAFETY NOTE NOTICE for all Audiolab amplifiers check the
clearance of the chassis screw that protrudes into the area of the mains
switch wiring
and REPLACE with shorter screw. This errant screw was the cause of the hum,
removing it and the hum went but the leakage ac remained so had to replace
the mains transformer.
Whether the leakage and screw problems were related i've no idea.
Replaced with 25-0-25V torroid and half wave rectified DC on main cap of 35V
innstead of 42V but seemed to work OK. There is little power used in a
pre-amp
so I assume it is only there to give weight - the customer requires some
mass
for his money as well as functionality.

 

[Mark D. Zacharias]

I'm getting a barely discernable "buzz" between the 10 and 12 o'clock
positions on the volume pot of my Denon PMA-520 integrated amp. I
cleaned with Deoxit, no change. Does this indicate there is a bad
spot on the pot, or could it be something else? The pot has the
following written on it:

2110524005-100K??x2

The ?? are some weird character, might be a japanese letter or
something. The pot is made in japan.

I've had just a few pots that did not respond to normal cleaning, but
finally did, with more aggressive cleaning technique.

In my case, I used an air compressor aimed at the carbon element, used more
De-Oxit and Caig D-100L, worked it some more, hit it with the compressor
again, etc. After several tries the pots finally responded to the treatment.
Maybe there was some crud physically adhered to the carbon element - who
knows?


Mark Z.

 

[N Cook]

A simple way to confirm/eliminate is temporarily solder say a 50K between
wiper and one end , for each pot, and see if the problem spot moves.

If still the same area of pot after R addition and no track problem then
this amp also had similar problem if the buzz was mains bourne triac noise.
Ground and faux ground with the wiper getting too close to the pot casing

Ashdown ABM500 bass amp, 1997
on my repair brief file
http://www.divdev.fsnet.co.uk/repair2.htm

 

[[email protected]]

I'm getting a barely discernable "buzz" between the 10 and 12 o'clock
positions on the volume pot of my DenonPMA-520integrated amp. I
cleaned with Deoxit, no change. Does this indicate there is a bad
spot on the pot, or could it be something else? The pot has the
following written on it:

2110524005-100K??x2

The ?? are some weird character, might be a japanese letter or
something. The pot is made in japan.

I'm only getting this buzz (more of a buzz than a hum) on the left
channel. On other portions of the sweep, it is dead quiet. On the
right side, I get some very minor white noise once I turn up the amp
way up, much more than one would do with speakers connected (I'm using
headphones). The buzz and white noise are actually quite low and not
really bothersome, but they are there.

What pot supplier did Denon use during this period, 1994 or so I'm
guessing? Does the model number give some indication of the
manufacturer? I've contacted tritonics to see what they say about
availability, but would rather fork over a couple of bux.

The pot has two sets of four pins. The resistor being spoken of would
attach between which pins?

 

[[email protected]]

I'm getting a barely discernable "buzz" between the 10 and 12 o'clock
positions on the volume pot of my DenonPMA-520integrated amp. I
cleaned with Deoxit, no change. Does this indicate there is a bad
spot on the pot, or could it be something else? The pot has the
following written on it:

2110524005-100K??x2

The ?? are some weird character, might be a japanese letter or
something. The pot is made in japan.

OK, got an estimate on the part from Tritonics:

The part number for location VR401 is 2110524005 - Special Order -

$11.34 plus shipping and handling and sales tax, if applicable.

Tritronics, Inc. Parts

 

[Arfa Daily]

OK, got an estimate on the part from Tritonics:

The part number for location VR401 is 2110524005 - Special Order -

$11.34 plus shipping and handling and sales tax, if applicable.

Tritronics, Inc. Parts

For that money, it's worth just 'going for it', if for no other reason than
to prove it one way or the other. I am dubious that it is going to be the
cause of the trouble, though ...

Arfa