Rickenbacker RM112P monitor amp intermittnet popping and crackling.

[David Farber]

This Rickenbacker RM112P monitor amp came to me with the complaint that it
randomly crackles and pops. I plugged it in this afternoon and of course it
didn't make any pops or crackles. I disassembled it and cleaned the
controls. They were only slightly noisy. I was unable to locate a schematic
for it. If it does decide to break down and make the noises, I would like to
be able trace the signal. Does anyone have a link for a schematic? It's very
clean inside. There are a few potential problem places that I see. One is
that there is double sided sticky tape holding the filter capacitors in
place. The p.c. trace is not insulated and I was wondering if that could be
causing a problem. Secondly, there seems to be some type of chemical
reaction happening leaving a flakey orange substance where some of the
components are connected to the circuit board.

http://webpages.charter.net/mrfixiter/images/Electronics/Rickenbacker/Flakey-terminals.jpg

http://webpages.charter.net/mrfixiter/images/Electronics/Rickenbacker/Filter-caps.jpg

Thanks for your reply.
--
David Farber
Los Osos, CA

[N_Cook]

What date?
Assuming >2006 then first diagnostic procedure is to waft a bird feather
around the components while powered up, if you've not been manually
touching things inside.

[pf...@aol.com]

I would suggest you re-solder those two resistors - making sure that the leads have not corroded to any degree. Ideally, replace them and clean the solder traces. I use an electric eraser for this purpose.

https://www.artsuppliesonline.com/prodimg/6150.jpg

With a very soft insert. Wonderful devices that do not 'pull' traces or leave conductive scarf.

I expect your problem is thermal - and due to vibrations when hot. So, get the thing going, and using a wooden stick - something like a drumstick, tap the various components and see where you get a reaction. Clean that up, and you will be fine.

Peter Wieck
Melrose Park, PA

[tabb...@gmail.com]

Poor connection. Tap around gently with an insulating stick to locate it.


NT

[Wond]

Looks like the filter cap lead in the middle of the pic may not be
soldered properly!

[David Farber]

There is no date that I could find on the unit. I called the Rickenbacker
company in Santa Ana, CA, and was told they don't have schematics for the
older amplifiers. They couldn't even tell me the manufacturing date of the
amplifer when providing them the model number. My educated guess is that
it's from the1990's or older.

[Phil Allison]

David Farber wrote:

------------------------

** Good servicing practice requires that you FIRST observe a fault before delving inside to find the cause.

Consider that the unit may have no fault at all, the reported noises being fed in from an external device and / or are due to AC supply transients.


.... Phil

[David Farber]

Hi Phil,

I would agree with you up until the point where after several days of
waiting, and no faults are exhibited, then a peek inside the unit might give
you a clue. Maybe something spilled inside, or perhaps another tech might
have done some creative repairs. I haven't mentioned until now but I did
find this (photo links below) sitting in the wide open space below the
speaker inside of the amp box. I don't think it belongs inside the amp. But
even if it's loose inside, I still don't think it would cause popping and
crackling noises. Can you identify what it is? It looks to me like it is
from a wall attachment for a telephone.

View 1
http://webpages.charter.net/mrfixiter/images/Electronics/Rickenbacker/Mystery-object-a.jpg

View 2
http://webpages.charter.net/mrfixiter/images/Electronics/Rickenbacker/Mystery-object-b.jpg

[Phil Allison]

David Farber wrote:

-------------------

> >
> > ** Good servicing practice requires that you FIRST observe a fault
> > before delving inside to find the cause.
> >
> > Consider that the unit may have no fault at all, the reported noises
> > being fed in from an external device and / or are due to AC supply
> > transients.
> >
> >
> > .... Phil
>
>

> I would agree with you up until the point where after several days of
> waiting, and no faults are exhibited, then a peek inside the unit might give
> you a clue. Maybe something spilled inside, or perhaps another tech might
> have done some creative repairs.
>

** The flaw with that idea is that you will very often find something odd looking and wrongly assume it must be the cause of the reported fault - when it is not.

False alarm reports are VERY common with guitar amps and accessories plus also with disco equipment and PA gear.

If after a reasonable time running and testing a unit, it shows no sign of the reported fault then it becomes the owner's problem to DEMONSTRATE the fault to the repairer.





.... Phil

[pf...@aol.com]

The difference is: An amp in service is loaded, unloaded, lifted, carried, vibrated, kicked, and otherwise physically abused.

An amp in the shop sits quietly on a bench or on a shelf with nothing to disturb it.

A customer who puts equipment into the hands of a tech - and is thereby spending money has no reason to create a false (and possibly costly) alarm. An Honest Tech is obligated to take the customer at their word. Hence the advice to check for visible defects, to tap the parts with a diddle-stick or similar - in other words, go looking for trouble. Further, and Honest Tech who has been around a while will kinda-sorta have a good idea where to start based on historical experience. And an Honest Tech, when confronted with obvious 'not right' things will correct them - within the minimum charge limit at the very least.

[David Farber]

Hi Peter,

I am doing this as charity work for a local Jazz group. I occasionally play
with the group at their Vets' Hall in Pismo Beach, CA. http://pismojazz.com/
I know the people there very well and the person that gave me the amp to fix
told me how it failed during a concert last month. As was previously stated,
the problem could be external to the amp. When I continue testing it today,
I'll include lots of tapping and prodding to see if anything unusual occurs.

By the way, are you able to identify this "extra" part that I found inside
the box?

[dansabr...@yahoo.com]

Make sure that you clean the 1/4 inch jacks as well. I have seen poor connections here cause noise.

Dan

[pf...@aol.com]

On Thursday, November 9, 2017 at 3:19:06 PM UTC-5, David Farber wrote:

> I am doing this as charity work for a local Jazz group. I occasionally play
> with the group at their Vets' Hall in Pismo Beach, CA. http://pismojazz.com/
> I know the people there very well and the person that gave me the amp to fix
> told me how it failed during a concert last month. As was previously stated,
> the problem could be external to the amp. When I continue testing it today,
> I'll include lots of tapping and prodding to see if anything unusual occurs.
>
> By the way, are you able to identify this "extra" part that I found inside
> the box?
>
> View 1
> http://webpages.charter.net/mrfixiter/images/Electronics/Rickenbacker/Mystery-object-a.jpg
>
> View 2
> http://webpages.charter.net/mrfixiter/images/Electronics/Rickenbacker/Mystery-object-b.jpg
>
> Thanks for your reply.
> --
> David Farber
> Los Osos, CA

Short answer, no I have no clue. Much longer answer: I just installed half-a-dozen sharps containers in one of our practices, and if that device were 14" across and about 8" deep, it would bear an uncanny resemblance to the baseplate. That mounts to a wall or counter, and the container snaps into it and may be locked in place with a key. A tool is used to depress the cam (black sprung device) to remove the container.

Every so often, they let me out of the office and into the field to troubleshoot everything from tattoo-removal lasers to electronic door locks. Those things requiring certifications (lasers and surgical or treatment devices, cryostats and such) I will diagnose so that the certified repair technician has a starting point, usually with that tech on the phone. Those that do not, I will repair and test. So, rather than calling an outside carpenter, I installed the sharps containers as I was in the area. New Jersey, Texas, Oregon, Virginia, North Carolina, Georgia - it does get me around. But the resemblance is very close.

[Gareth Magennis]

wrote in message
news:1995a61e-77a6-4248...@googlegroups.com...

*************************************************************************************************************



It is not uncommon for customers to be fooled into thinking a piece of
equipment is faulty when it is not.
It is often not within their skillset to be able to reliably diagnose these
things, and they jump to erroneous conclusions.
You cannot always rely on their evidence, you often have to rely on your
past experiences as a professional instead.

If a customer brings me an amp with allegedly intermittent problems, it does
not sit quietly on my bench while I wait a day for it to go wrong.
I will poke and bang the fuck out of it to try and make it exhibit some
crackling or other such noise.
If it doesn't, then I will begin to suspect the fault is elsewhere.


Very often intermittent problems are down to switched jack sockets having
dirty contacts.
FX returns, Inserts, headphone sockets that cut the speaker, are prime and
very, very common suspects to be checked first.



Gareth.

[David Farber]

Hi Gareth,

I will give those jacks a good cleaning along with the other things you
mentioned.

[Phil Allison]

peter fuckwit puked:

--------------------

> >
> > > >
> > > > ** Good servicing practice requires that you FIRST observe a fault
> > > > before delving inside to find the cause.
> > > >
> > > > Consider that the unit may have no fault at all, the reported noises
> > > > being fed in from an external device and / or are due to AC supply
> > > > transients.
> > > >
> > > >
> > > > .... Phil
> > >
> > >
> > > I would agree with you up until the point where after several days of
> > > waiting, and no faults are exhibited, then a peek inside the unit might give
> > > you a clue. Maybe something spilled inside, or perhaps another tech might
> > > have done some creative repairs.
> > >
> >
> > ** The flaw with that idea is that you will very often find something odd looking and wrongly assume it must be the cause of the reported fault - when it is not.
> >
> > False alarm reports are VERY common with guitar amps and accessories plus also with disco equipment and PA gear.
> >
> > If after a reasonable time running and testing a unit, it shows no sign of the reported fault then it becomes the owner's problem to DEMONSTRATE the fault to the repairer.
> >
> >
> > .... Phil
>
>
> The difference is: An amp in service is loaded, unloaded, lifted, carried, vibrated, kicked, and otherwise physically abused.
>
> An amp in the shop sits quietly on a bench or on a shelf with nothing to
> disturb it.

** Not in my shop it don't !!!

> A customer who puts equipment into the hands of a tech - and is thereby
> spending money has no reason to create a false (and possibly costly) alarm.

** Irrelevant garbage.

> An Honest Tech is obligated to take the customer at their word.

** Only a stupid tech believes that garbage.

> Hence the advice to check for visible defects, to tap the parts with
> a diddle-stick or similar - in other words, go looking for trouble.
>

** In my shop, "testing" involves a full range of operation and performance checks - including some rough treatment plus tapping on PCBs and tubes while running at full power and idle.

The OP here has a simple SS monitor amp with a vague complaint of pops and crackles that will not show.

My advice was 100% solid and professionl.

As bloody usual yours is the opposite.




.... Phil

[pf...@aol.com]

On Thursday, November 9, 2017 at 9:04:06 PM UTC-5, Phil Allison wrote:

> My advice was 100% solid and professionl.
>
> As bloody usual yours is the opposite.
>

Sure, you walk on water.

Get your meds adjusted.