Hi all. I recently had the original POTS for a musical fidelity A5 amp replaced with a Alps RK27 motorized POTS that I thought was an exact replacement as I had seen a few threads around where people had used this POTS.
I had the repair done by a repair shop who failed to tell me the Alps POTS was too big for the PCB, but boshed it on anyway. In short, the distance between the resistor pins and the motor pins is too long. He also messed up a capacitor and I am left with a loud buzz that's being picked up from the transformer and fed into the speakers. I'd bring it back, but Covid has kinda closed everything.
I do find myself screwed now. The POTS was inexpensive, but trying to find a motorized POTS to fit the PCB is a challenge. I looked at the TKD 2CP2511 but it's pins are placed 8mm apart vs 10mm on the PCB and are 15mm across vs. 10mm across on the PCB. The only correct thing about it is the distance from middle set of pins to motor pins if that makes sense?
On the other hand, the Alps fits all the dimensions bar front to back.
Has anyone any suggestions on motorized POTS' that might fit?
I had the repair done by a repair shop who failed to tell me the Alps POTS was too big for the PCB, but boshed it on anyway. In short, the distance between the resistor pins and the motor pins is too long. He also messed up a capacitor and I am left with a loud buzz that's being picked up from the transformer and fed into the speakers. I'd bring it back, but Covid has kinda closed everything.
I do find myself screwed now. The POTS was inexpensive, but trying to find a motorized POTS to fit the PCB is a challenge. I looked at the TKD 2CP2511 but it's pins are placed 8mm apart vs 10mm on the PCB and are 15mm across vs. 10mm across on the PCB. The only correct thing about it is the distance from middle set of pins to motor pins if that makes sense?
On the other hand, the Alps fits all the dimensions bar front to back.
Has anyone any suggestions on motorized POTS' that might fit?
Post up a picture of the old pot and we can help you identify it.
(NB it’s a ‘pot’ for potentiometer and not a POTS which is a totally different thing ‘Plain Old Telephone System’ and a term used in telecommunications).
🙂
(NB it’s a ‘pot’ for potentiometer and not a POTS which is a totally different thing ‘Plain Old Telephone System’ and a term used in telecommunications).
🙂
Cheers Bonsai. I don't have the old POT as the repair guy would have disposed of it.
Quick update though- when the POT is disconnected and moved away from the transformer, no noise.
I spotted some crud around the new solder and also on the PCB paths that I am going to deox and see what happens. Theres a less than ideal solder joint (exposed wire) where the live incoming mains joins the PCB at the power switch.
Quick update though- when the POT is disconnected and moved away from the transformer, no noise.
I spotted some crud around the new solder and also on the PCB paths that I am going to deox and see what happens. Theres a less than ideal solder joint (exposed wire) where the live incoming mains joins the PCB at the power switch.
OK. Piccs of both pot's attached. The two look identical but the older one is much shorter than the new.
The orientation of the pin on the front is also different. The old allowed for a horizontal PCB mount and the new one only allows for vertical mount. The new model is RK27112MC01P.
The orientation of the pin on the front is also different. The old allowed for a horizontal PCB mount and the new one only allows for vertical mount. The new model is RK27112MC01P.
Attachments
The pic on the RHS looks like a Alps Blue Velvet RK27 dual gang 50k log pot. I use the 10k version of that.
I don't know what the pot on the LHS is - I don't recognize it as an Alps pot.
For the pot on the RHS, here is the RS components part number
234-6617
The price is ~£16
I don't know what the pot on the LHS is - I don't recognize it as an Alps pot.
For the pot on the RHS, here is the RS components part number
234-6617
The price is ~£16
Hi Bonzai. Pot on the left is an ALPS pot alright. It’s the new one and it’s the same part code as the one you called out for the pot on the right. But it’s too big!
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Who did you buy it from? Or where did the technician get it?
The part from RS has a data sheet with measurements so it’s easy to confirm it’s right.
There are a number of Taiwanese and Chines companies making Alps lookalike pots.
The part from RS has a data sheet with measurements so it’s easy to confirm it’s right.
There are a number of Taiwanese and Chines companies making Alps lookalike pots.
Cheers Bonzai. Definitely Alps, bought from RS. The biggest problem is the distance from the resistor pins to the pins that hold the motor section to the PCB.
I’ve just ordered another to measure it up to the PCB as Alps don’t give the full measurements of the pot online. Close, but there are some important missing figures!
Actually, it does have the measurement but it is 30.5mm and the PCB holes are spaced about 20mm apart.
I can't find anything that will fit it unless I go to a non motorized model. Do hifi manufacturers use OEM's popular models which is the only thing I can think of now.
I’ve just ordered another to measure it up to the PCB as Alps don’t give the full measurements of the pot online. Close, but there are some important missing figures!
Actually, it does have the measurement but it is 30.5mm and the PCB holes are spaced about 20mm apart.
I can't find anything that will fit it unless I go to a non motorized model. Do hifi manufacturers use OEM's popular models which is the only thing I can think of now.
I think, from a check of various internal pics of the A5, that their ALPS pots may have very similar motor drive assemblies to the standard RK27 design of old but the pots themselves are distinctly smaller, even if similar in appearance. This would explain the need to bodge the fit.
See an image of the A5 version here: Musical Fidelity A5 Integrated - L2 Upgraded -- Superb Intergrated! Photo #1532893 - US Audio Mart
See an image of the A5 version here: Musical Fidelity A5 Integrated - L2 Upgraded -- Superb Intergrated! Photo #1532893 - US Audio Mart
Hi Ian. I think you're right. While the resistor pins are spaced 10mm apart the resistor body width is thinner. The new RK obscures all the PCB markings visible in the picture you shared making me think the only resolution is to have a new PCB made.
These aren't burn marks but solder rosin / flux . You can clean it with some solvent. I use Kontakt Chemie Flux off. Try alcohol or acetone. Be careful with plastic parts.
Last update and a positive one. I found an Alps pot that ‘looks’ bang on identical to the original and three times the cost of the RK27. In my haste to replace the pot, I forgot the motor was offset to the shaft and I didn’t take not of the exact pin placement.
So, sadly, my hell continues. New POT arrived today, perfect size match, 50KAX2 as per the original, removed the old soldered in the new and..... It goes from deafening to deafening.
I assume the resistors must be screwed?
I assume the resistors must be screwed?
I was looking for input as to a possible problem with the new potentiometer that I bought that is providing no control over the volume at all.
If i understand what you want to tell in an obscure way there is no change in volume when the
knob of the "POTS" is rotated. I assume you have output, but too high.
If so the ground connection is missing. This is on the two outside POTS PINS in counter clockwise
position. Use an ohmmeter.
Next post .. how can I find and use one ?
knob of the "POTS" is rotated. I assume you have output, but too high.
If so the ground connection is missing. This is on the two outside POTS PINS in counter clockwise
position. Use an ohmmeter.
Next post .. how can I find and use one ?