i'm a complete novice and this is my first build. I essentially followed the DIY guide like a cake recipe. Made a mistake and soldered the Peter Millet potentiometer board upside down and then damaged the pot trying to separate. Salvaged the board I think and ordered a new potentiometer on ebay which just arrived. Put it all together and it powers up fine, and works but the R line out channel is not working. Both inputs work with two different sources and changing RCA cables did not rectify the problem.
Voltages
T1 23.86 V
T2 23.11 V
T3 22.35 V
T4 8.87 V
T5 610 mV
T6 621 mV
T7 and T8 dialled to 9.5V
Not sure what to do.
Any help appreciated!
Voltages
T1 23.86 V
T2 23.11 V
T3 22.35 V
T4 8.87 V
T5 610 mV
T6 621 mV
T7 and T8 dialled to 9.5V
Not sure what to do.
Any help appreciated!
The voltages look good so the board is probably good.
You should have a good look at the input selector switch. Check that the wiring is correct and the soldering is good. It looks like there are exposed wires so check to make sure that there are no shorts between signal wires and ground wires.
Check that the wiring from the selector switch to the pot board is correct. Make sure that the signal wires are at the correct positions and the ground wires are at the correct positions. The wire connections to the pot board are not clear. It may be that the R ground and R signal from the selector switch are not at their correct positions on the pot board.
You should have a good look at the input selector switch. Check that the wiring is correct and the soldering is good. It looks like there are exposed wires so check to make sure that there are no shorts between signal wires and ground wires.
Check that the wiring from the selector switch to the pot board is correct. Make sure that the signal wires are at the correct positions and the ground wires are at the correct positions. The wire connections to the pot board are not clear. It may be that the R ground and R signal from the selector switch are not at their correct positions on the pot board.
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Thanks Ben. I had a good look at the selector switch and the potentiometer wiring. As far as I can see it looks good and is wired correctly. Could it be that I have damaged the RK27 PCP circuit board that sits on top of the pot?
check input selector switch with ohmmeter
these are easy to melt, contact stud moving in plastic and there is no proper contact
simple logic - compare measurement of good channel/section with not working one
inform here
btw - while preamp is playing some music (not loud) you can poke with small screwdriver tip to deliberately make short between mid stud and any of outer ones , on said switch
you can make mono same way (tweezers, short two mid studs) - plenty of things - to decipher where culprit is situated
these are easy to melt, contact stud moving in plastic and there is no proper contact
simple logic - compare measurement of good channel/section with not working one
inform here
btw - while preamp is playing some music (not loud) you can poke with small screwdriver tip to deliberately make short between mid stud and any of outer ones , on said switch
you can make mono same way (tweezers, short two mid studs) - plenty of things - to decipher where culprit is situated
ZM is fast and most certainly has much better suggestion than I was going to make.
I was going to suggest you can verify potentiometer circuit board is good with quick check of continuity from each wire(s) to pot post(s) The top traces don't look damaged (few nics) and only one trace is on bottom.
I was going to suggest you can verify potentiometer circuit board is good with quick check of continuity from each wire(s) to pot post(s) The top traces don't look damaged (few nics) and only one trace is on bottom.
while playing softly:
short two mid studs on selector switch with tweezers- if you get sound to both channels - replace switch, careful soldering please
short two mid studs on selector switch with tweezers- if you get sound to both channels - replace switch, careful soldering please
ok I got about 150-160 ohms across the blue and blue and white , similar on the brown and brown and white, and OL on the orange and orange and white.
Tried to short and didn't seem to make a difference.
[Edited] I'm gonna get outta the way and let ZM help you. He's gonna be better at this than I am by miles and miles. Or kilometers x 1.6.
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now - gentle play of music - short with tweezers two input pads on pot pcb
best to have isolated tweezers from your hand, to not induce hum by fingers; use some tape or heatshrink if need to isolate them
if you don't get second channel that way, then
short two mid pins of pot ( outputs to preamp pcb)
inform here
edit: what birdbox said - input selector switch - as shown on pic - vertically divided - left is one channel, right is other channel
mid stud on both is output to pot
upper studs are wires from one input RCAs
bottom studs are wires from second input RCAs
if you want to test mono - tweezers - connect two mid studs
if you want to test contact to present input - connect mid stud with either top or bottom stud on same side
best to have isolated tweezers from your hand, to not induce hum by fingers; use some tape or heatshrink if need to isolate them
if you don't get second channel that way, then
short two mid pins of pot ( outputs to preamp pcb)
inform here
edit: what birdbox said - input selector switch - as shown on pic - vertically divided - left is one channel, right is other channel
mid stud on both is output to pot
upper studs are wires from one input RCAs
bottom studs are wires from second input RCAs
if you want to test mono - tweezers - connect two mid studs
if you want to test contact to present input - connect mid stud with either top or bottom stud on same side
Thanks Birdbox- I'm really not very good at this. I appreciate your help. I was getting OL on the meter with both poles.
Zen Mod- I got both channels working with some hum ( with slightly dodgy insulation holding heatshrink with tweezers) when I shorted B out (blue) and A out (orange) on the R27 PCB
Zen Mod- I got both channels working with some hum!! ( with slightly dodgy insulation holding heatshrink with tweezers) when I shorted B out (blue) and A out (orange) on the R27 PCB
it is, if shorting two inputs on pot invoke sound on Dodo channel
if shorting inputs is not working but shorting outputs works, then pot is either toasted or badly soldered (anything on its pcb)
now, that not excluding toasted switch possibility
who sez that 2 or more mistakes are impossible
fragility of these small switches is well known - nothing to worry when you have mileage in soldering, but prior to that, one is having all chances to ook it big
before proceeding with anything else - take ohmmeter and check for shorts directly on input RCA of channel in question
black probe on RCA GND, red probe on RCA hot - you must read same as on proper channel
if said input is not selected with input switch ( not seeing vol pot) it must show open circuit
if said input is selected , it must show approx 50K (vol pot value)
if everything OK there, you can proceed - resolder everything on pot pcb;
if that not helps, time for changing the pot
now - do you have an idea how to check pot with ohmmeter, is it functional/ having proper readings with ohmmeter?
I/we can lead you step by step, but it'll be better for you to invest some time, to actually grasp what's pot, it's role and function and how to do few measurements
black probe on RCA GND, red probe on RCA hot - you must read same as on proper channel
if said input is not selected with input switch ( not seeing vol pot) it must show open circuit
if said input is selected , it must show approx 50K (vol pot value)
if everything OK there, you can proceed - resolder everything on pot pcb;
if that not helps, time for changing the pot
now - do you have an idea how to check pot with ohmmeter, is it functional/ having proper readings with ohmmeter?
I/we can lead you step by step, but it'll be better for you to invest some time, to actually grasp what's pot, it's role and function and how to do few measurements
thanks Zen Mod. I'm going to have to leave this for a couple of days but will report back when I have investigated yours and BirdBox's suggestions. Thanks for helping me with this- so frustrating! But great to have people that know what they are talking about to help me. Cheers!
Those dirty little switches. I got to the point that I prewired them and added heat shrink on top of that. Maybe next time, I will find a switch with wire wrap posts. No heat, but I 'sting' them with a bit of solder anyway. Trust nothing.
Thank you @birdbox and @Zen Mod !! I did as you suggested above. Was not getting any continuity between the circled pot pin and AIN, used tweezers to connect and started getting sound in the bad channel, soldered a jumper wire and now it's working!! I would never have got there without your help. Fantastic!
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