New Clarinet...Help

Quicksilverproac · « **Reply #20 on:** 10 Jun 2013, 11:44 pm »

I changed the tubes...found one was a 12ax7.... the voltages are back in range. I think I pulled the tubes from the Cornet without thinking one was a 12ax7.

poty · « **Reply #21 on:** 11 Jun 2013, 06:41 am »

You still have not said about checking the input circuit (R302 and so on).

Quicksilverproac · « **Reply #22 on:** 11 Jun 2013, 12:53 pm »

There is a zero or .1 reading across r302....turning the volume does not change it.

poty · « **Reply #23 on:** 11 Jun 2013, 04:41 pm »

That is it! Find what short-circuits the resistor and your problem will be definitely solved!

Quicksilverproac · « **Reply #24 on:** 11 Jun 2013, 06:56 pm »

I pulled out the two R302 330k's and a traced ..the best I could. Looked for solder etc....put the the R302,s back...still nothing . i went over the volume control and switch....Could it be the rca's or the tube socket?

poty · « **Reply #25 on:** 11 Jun 2013, 08:27 pm »

There are balance and volume controls between the RCA and the R302, so even if you short-curcuited RCAs you won't have zero reading.
There is R303 between tube socket and the R302 so you'll have 220 Ohm at minimum.
Are you shure you measured the resistance correctly? It could be 330 Ohm (not 330 kOhm) and you tried to measure on kilo-ohm scale.
If all measurements are correct then something has to be wrong.

Addition: could you post a close photo of the place where the R302 resides? On your posted photo this area is obscured by huge capacitors.

Quicksilverproac · « **Reply #26 on:** 11 Jun 2013, 09:29 pm »

bregez · « **Reply #27 on:** 11 Jun 2013, 11:57 pm »

A little constructive criticism here. I would flow those solder joints more, the clarinet board has through hole plating so you really want to take advantage of that and flow solder in the hole. Secondly, with long leads on the resistors there is an increased chance of picking up unwanted hum or noise.

Brad

poty · « **Reply #28 on:** 12 Jun 2013, 11:15 am »

At first glance all seems OK. Is it possible that either the jumper in place of C302, the top wire of R302, left wire of R303 or the run of the volume pot somehow touch the ground? (top, left and so on - according to the schematic)

Quicksilverproac · « **Reply #29 on:** 12 Jun 2013, 01:46 pm »

I went through it again... could not find a short to ground. I rechecked the voltages and they are all close...however when I rechecked the pins 1 and 6 to corresponding c300...zero , and pins2 to gnd & 7 to gnd 47ohms. I also reflowed all the solder as suggested.

poty · « **Reply #30 on:** 12 Jun 2013, 02:41 pm »

First thought: is your tester OK?
Second thought: maybe the Vishays are problematic?
As far as the voltage readings are OK I'd put all my attention to input circuit. Do the tests on one channel to minimize impact from resoldering. Remove the jumper in place of C302. This creates two unconnected circuits: R302, 303, V300 and RCA, switch and two pots. Repeat the measurements across the R302 and the other side of C302 to ground (the volume pot should be at max volume). If the reading across the R302 is zero, then the shorting is directly at the signal side of R302 or input side of R303. If the other reading is zero, then the problem is either in the volume pot or how it is soldered.

bregez · « **Reply #31 on:** 12 Jun 2013, 03:38 pm »

This is a long shot. Have you checked the tube sockets? Some of the Chinese made sockets use very thin, brittle and barely conductive substrate metal. Maybe there is an internal break? The plating on the substrate may also delaminate causing all kinds of weird noises and hums that are difficult to diagnose. This is most common with the gold plated ceramic variety.

poty · « **Reply #32 on:** 12 Jun 2013, 04:14 pm »

Brad, if it was the socket the resistance measurement across R302 would be at least 220 Ohm. I doubt it is the socket.
My most probable guess - the volume pot: either it is soldered wrongly or it is bad itself (this possibility including wrong part number / solder footprint). This guess is supported by the fact that it is for both channels. Other things are less probably so symmetrical in nature.

bregez · « **Reply #33 on:** 12 Jun 2013, 04:34 pm »

Good point Poty. I think the Panasonic EVJ-C20F02A54 (digikey P2T3503-ND) volume pot was discontinued. Jim had suggested substituting with a Panasonic EVJ-C25F02A54 (digikey P2Y7503-ND). They look compatible electronically:
http://industrial.panasonic.com/www-data/pdf/AOK0000/AOK0000CE9.pdf
However, the new version has a nylon sleeve and will not ground to the chassis.

Quicksilverproac · « **Reply #34 on:** 12 Jun 2013, 04:46 pm »

The volume pot seems to be soldered correctly...it is not the one thats called for in the BOM. It should be the same with the exception of the plastic shaft. The meter beeps when the probes are on the end pins. The other pins are open. How can I tell if the pots bad? Maybe Mosher has the correct pot. I do have the gold plated ceramic sockets.

bregez · « **Reply #35 on:** 13 Jun 2013, 04:03 am »

To test the volume pot in-situ do the following:

1) Unplug power and cables into the clarinet.
2) The pot is a 50K ohm, so set your multimeter appropriately.
3) Place the common (black) wire from the multimeter to the ground lug on the back of the clarinet.
4) Place the red wire from the multimeter on your c302L jumper
5) With volume control all the way down, meter should read 0 ohms
6) Turn volume control up, the meter should read 50K ohms (make sure balance control is centered)
7) Repeat Steps 4-6 for c302R

Hope this helps.

poty · « **Reply #36 on:** 13 Jun 2013, 06:47 am »

You have a problem, so the suggestions above you should do with the C302 jumpers removed.

Quicksilverproac · « **Reply #37 on:** 13 Jun 2013, 05:27 pm »

I removed the jumpers from C302... the inside cap wires beep to gnd. R302 measures 330Ohm...not K however I removed one yesteday and it was 330K....not sure ... I have a few Kiwame 220's. If the Vashays are a problem which ones would you replace. The Volume pot seems ok 50K and tuns down to near zero.

bregez · « **Reply #38 on:** 13 Jun 2013, 08:41 pm »

Inside cap wires should only beep to ground with the volume control turned all the way down.
Both R302 resistors should be 330K ohms. You should be able to measure on the board. Check your meter for decimal placement.
In the past Kiwames were just re-branded KOA Speer carbon film resistors. The KOAs can be bought at mouser for under fifty cents. Not sure if this is still true however.

Quicksilverproac · « **Reply #39 on:** 13 Jun 2013, 09:02 pm »

The inside cap wires beep all the time...with the volume pot all the down and all the way up. I am not sure whats going on with the 330K resistors...they measure 330 ohms ...all the other 330k's measure 330K. I am using a Fluke 777....not sure whats happening.