[david62]

There could be a wiring mistake on the RCAs on the input side.Would a input reversal on the input side still cause the output channel balance control to be reversed to the power amp and speakers?

[poty]

It is possible. The balance control is on the INPUT side, not output.
Addition to the above: if you unplug the left INPUT interconnect what channel disappears at the output? I have a feeling that it will be the right channel at the output. If not - there may be great general mistake in input wiring.

[david62]

With the C302L and C302R positions jumped,the sound was balanced,mono.Tomorrow I will disconnect one input plug and see if the correct channel is witout sound.
David

[david62]

I removed the jumper between 302 L and 302R and it is back being heavy in the left channel and I need to turn the balance control to the left to between 9 and 10 O'clock to have it balanced.I also removed the left input plug from two of my input sources which caused the left speaker to be silent and only the right producing sound.I'm not sure what explains this situation.On the plus side,the Clarinet sounds really nice so lond as I adjust the balance control.
Dave

[poty]

I removed the jumper between 302 L and 302R and it is back being heavy in the left channel and I need to turn the balance control to the left to between 9 and 10 O'clock to have it balanced.

This means you have to check the input parts and wirings up to C302s (including input RCAs, selector S300, balance pot R300, volume pot R301). Get your DVM and trace the wiring from the input RCAs to S300 and the ground, the connection of the S300 to R300 and further to R301 and the connection of the R301 to C302. All the tests you can do in resistance measuring mode. For example, one probe from the DVM (the Clarinet should be switched off!) to the center contact of RCA, another - to the corresponding channel's C302 (the lead going to the volume pot). You should have from 0 to 100k of resistance, you should have the ability to change the readings by volume control in the 50k margins and by balance control in the same margins. If you put one probe to the RCAs' shell and the other to the C302 you should have from 0 to 50k readings changeable by the volume pot.

I also removed the left input plug from two of my input sources which caused the left speaker to be silent and only the right producing sound.

OK, IMHO this means that you entangled both input and output wirings. It's easy to detect. Put a jumper across R302L - the left channel should go in silence.

P.S. By writing "entangled" I mean: The RCAs with white color you connected to the right channel (where the parts have numbers ended in "R"), right colored RCAs you connected to the left channel (where the parts have numbers ended in "L") on both (input and output) sides. While the channels are identical there are parts common to both channels (balance pot) and wrong connection can lead to such strange things. It is not related to the volume difference between channels (but maybe the wiring mistake could bring the problem too)!

[david62]

 Poty,

     I want to again thank you for your time and expert advice.I will go back in with a ohm meter and measure as you suggest.I think that I will need to take the top cover off of the chassis.Hopefully the selector switch and two pots will hold the PC board to the front panel so I don't stress the wires off of the board to the RCA's.I think there is enough slack in the transformer leads to allow a small lift of the top cover and then I can rotate the top cover to access the top of the board.I will then also be able to see the solder joints on the pots and selector switch.I probably will not have the time to work on it until this weekend.In the mean time,it sounds very nice.
Dave

[david62]

 I did find some bad resistors. R107,R302,R312 are all Kiwami 330k.R312 R

[david62]

I did find some bad resistors. R107,R302,R312 are all Kiwami 330k.R312R and R312L are both open.The other 330k's are way off and measure between .86K and 1.2k.I'm surprised that the whole batch of 330K resistors that I used were bad or went bad.Before I order replacements I will measure all of the resistors!
Dave

[poty]

Dave,
If you measured the resistors already soldered into PCB - you may measure the complex resistance of the resistors and other parts in the schematic. So, for the beginning, try to measure the way I suggested earlier and then we will try to find the source of the problem.
The only strange thing: R312R and L must not be open! Are you sure you choose the right scale on your DVM and measured at the right points? As far as the R312s are the only DC resistance at the output you can measure resistance right at the output RCAs (one probe to the center pin, the other - to the ground (shell) point.

[david62]

 I put a new battery in my multimeter and still have some inconsistencies in the ohm measurements,but no longer get any open circuits.I ordered a new multimeter and will re-measure with a new meter when it arrives.I decided to replace the battery in the meter because it didn't make sense to have open circuits when the voltage measurements are pretty close to spec.The inconsistencies in measurements may be as you pointed out,due to the resistors being connected to other components in the circuit.I should have the new meter by the end of the week.
Dave

[david62]

I checked the input cobbections to the selector switch as well as the volume and balance pots which were all fine.My plan is to change the 5 watt 3 ohm resistor to 2.7 ohms to raise the heater voltage from 5.72 volts to closer to 6.3 volts. Since the 1uf caps were in reverse polarity on the weaker channel,I will switch them.If the left channel remains slightly weaker,I will just live with it.I should have the new 5 watt resistor next week.
Dave

[poty]

Could you elaborate more about what you've done and what you've got?

[david62]

I checked the connections between input RCA and that channels C302 and turned the volume and balance pots.With one lead in right channel input RCA and the other on C302 (which is a jumper on my board)when I turn the balance control  to the right the resistance increases and reistance decreases turning the balance to the left.It is the opposite for the left channel.Checking the volume pot the same way gives consistent readings on both input channels.The solder joints look good for volume pot,balance pot,selector switch and connections check out well to traces on board and R300 to S300.

[poty]

I'd like to clear some things:

C302 (which is a jumper on my board)

This means you use jumpers instead of C302s?

I checked the connections between input RCA and that channels C302 and turned the volume and balance pots.With one lead in right channel input RCA and the other on C302 (which is a jumper on my board)when I turn the balance control  to the right the resistance increases and reistance decreases turning the balance to the left.It is the opposite for the left channel.

What you identified "that channels C302"? I mean if you check the right channel - how you know what of the two capacitors corresponds to the right channel? One more question: What is the values of the resistance measurements? It should be in the range of 0 to 100k. If they are more - it is possible that you measured both channels at once - just from each side. (I mean if you connect one probe to the left channel RCA and the other - to the right channel C302, then you would measure Left-RCA - S300 - R300L - R301L - ground - R301R - C302R.)

Checking the volume pot the same way gives consistent readings on both input channels.The solder joints look good for volume pot,balance pot,selector switch and connections check out well to traces on board and R300 to S300.

At what level you shorted out the inputs when you achieved the equal volume for both channels?

[david62]

 I used jumper wires in place of both C302's from the start.The left input RCA and C302 L jumper gave me readings about 0-100k,if I kept one lead on C302L jumper and moved the other lead to right RCA input it only read 0.The right channel input and C302 R jumper measured 0-10k as well.I did not have both channels connected for the above test,but two weeks ago I jumped both C302 jumpers and had equal volume from both channels.

[poty]

So you identified the "side" of the C302 looking at its index printed on the PCB?
Jumping between C302s shows than all parts after the point work well. So the only part of the circuit under question is between the RCAs and the C302s. Could you jump left and right RCAs and made the "equal volume test" with the jumper in?

[david62]

Poty,

     Yes, I used the PC board markings to id left and right C302's.For the volume test of jumping RCA's,do you mean the input RCA's?I am still waiting for a 5 watt resistor 2.7 ohms to replace the 3 ohm in the hope that it will raise the heater voltage from 5.7 volts closer to 6.3 volts.I know that the heater voltage is not the cause of the problem,but as long as it is on the bench,I may as well fix that too.

[poty]

Yes, I mean input RCAs. One jumper between the center pins of RCA should be enough.
Relating the "side" markings. The only thing I can think of is what do you mean "turn the balance left and right"?

[david62]

I mean position the balance pot control either toward the right or toward the left from the center point.When I change the 5 watt resistor,can I measure the heater voltage without any the 12au7 tubes in place,or should they be inserted?

[poty]

I mean position the balance pot control either toward the right or toward the left from the center point.When I change the 5 watt resistor,can I measure the heater voltage without any the 12au7 tubes in place,or should they be inserted?

No, you will have to insert all tubes, because the heater voltage is not regulated (changes with the amount of load and the mains voltage).
Relating the balance pot... I can't say exactly if the mirrored behavior is on purpose... If all tests have been done right it is the only explanation comes to my head.