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.
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.
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.
formatting link
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.
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.
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.
** 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.
looking and wrongly assume it must be the cause of the reported fault - wh en it is not.
also with disco equipment and PA gear.
f the reported fault then it becomes the owner's problem to DEMONSTRATE the fault to the repairer.
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 di sturb it.
A customer who puts equipment into the hands of a tech - and is thereby spe nding money has no reason to create a false (and possibly costly) alarm. A n Honest Tech is obligated to take the customer at their word. Hence the ad vice 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 star t based on historical experience. And an Honest Tech, when confronted with obvious 'not right' things will correct them - within the minimum charge li mit at the very least.
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.
formatting link
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?
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 b aseplate. 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 trouble shoot 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 technicia n 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.
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.
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 f*ck 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.
** Irrelevant garbage.
** Only a stupid tech believes that garbage.
** 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.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.