Resistance help with B3 now with a Hum on Left Channel

[wullymc]

hi there,

All finished my Beepre.  Did the resistance checks and everything is ok except for the following:

B3   - I can't seem to get a reading from this.  It just displays 1.  I was able to get a reading for A3 and was able to adjust the value using the volume control  (Manual - B3, A3 - varies with volume/balance settings, could be 0 to 50k)

I have gone back and looked at the wiring for B3 compared to A3.  I have also reflowed all the connections to the volume and balance controls and well as A, B, C, D of the selector terminals, and finally reflowed B3

I have gone over the wiring again for the B3 as well as for the selector, balance, and volume controls.

Any suggestions?  How can I check the volume and balance controls for amounts using my multi-meter.

Thanks....Dave

[Paul Birkeland]

Are the tubes installed when you're doing this by chance?  If so, you may have one socket in backwards, which would throw off your readings.

With the volume control all the way down, you should get close to 0 Ohms.  You can follow the wire from B3 back to the pot, then check the pot lug resistance itself.  The lug next to it with the black wire is grounded, so it should always read around 0 Ohms.  If it does not, that may be your problem.

-PB

[wullymc]

Hi Paul,

Thanks so much.....Solved!  For some reason the ground at 8 wasn't giving me a value at B3.

In trying the ground connection on the pot and the white connection on the pot and then at B3 everything worked out.


Thanks so much.  You are always there for us here.  Appreciate it.....Dave

[wullymc]

Okay!

Very exciting the tubes lit up and so did all 8 leds!!

Took the voltages and everything looks good the only questionable one I have is:

Terminal 17    read  81V    (manual says should be between 90-110V)
and corresponding B2 is also 81V (manual says should be between 90-110V)

These fall within the 10-15%

the other terminal on the other side is:  Terminal 2 which read 103V  (manual says should be between 90-110V)
and corresponding A2 is 102V (manual says should be between 90-110V)

I plugged in the amp and have a deep hum on the left channel.  I swapped tubes around but the hum is still present on the same side.

I looked through some threads with regards to hum with the Beepre.

I reflowed and added solder to 28-31, top and bottom, as well as the lug on the transformer that the big diodes connect to.  Still the hum remains.

I have taken voltages for the following:

                                L                     R
Pos In                       13                   13
Pos Out                      9                     9
IB                            146                  146
OB                             81                  102
IA                            184                  185
OA                           146                  146
Kreg                           3                     3
+reg                        146                  146


I am thinking that the hum is because of grounding on the left channel?  I am going to go back and follow the ground back from the left channel output and reflow all the
grounds and see if that takes care of it.  Hopefully so!

Any other suggestion would be very welcome!  Also, should I be concerned with the 81V at 17, OB, and B2?.....Thanks....Dave

[wullymc]

So i reflowed mostly all the terminals on the left channel.  REtook voltages and everything is good.


I plugged it in and again...hum.

I tried the different inputs and found that position 1 - loud hum in left channel, 3 small hum in left channel, 4 small hum in left channel and #2 no hum!!!

I think i found my problem.  i will reflow all the terminals in the selector switch and the r ca jacks.  YAY!

Thanks.....Dave....ps sounds good into a Lepai 2020 while my Paramounts are out for repair.

[wullymc]

hi there,

I did the chopstick test to the volume pot, bal pot, and selector switch.  The hum did not stop.

I also tested around and could not get the hum to stop or get worse.  This included the big diodes under the fil. reg board. 

If I have the selector switch on:

#1.  big hum on left channel
#2.  smaller hum than on #1 and if I tap the vol or bal or combination I can get the hum to stop on #2 but if I switch it to #1 the hum is back, switch to #2 and the hum isn't there
#3.  big hum on left channel
#4.  smaller hum on left channel.

If there was a problem with the left channel would the hum not be the same whether the selector was on #1,#2, #3 , or #4??  Why would there be a difference.  Could it be the selector switch?  Could there be a problem with the fil. reg board?  Here are the voltages from it:

                                L                     R
Pos In                       13                   13
Pos Out                      9                     9
IB                            146                  146
OB                             81                  102
IA                            184                  185
OA                           146                  146
Kreg                           3                     3
+reg                        146                  146


Thanks for your help....Dave

[Doc B.]

Are you shorting the inputs when you do this test?

[Paul Birkeland]

I believe there is still something a bit wrong with your grounds.  What resistance do you get between the chassis plate and each lug on the level control with a black wire connected to it?

[wullymc]

Hi Doc, Paul,

Thanks for your replies.

I haven't been using shorting plugs.  I unfortunately don't own any.

As for the resistance values of the black wires, they are:

Selector Switch:  B    1 (infinite) - can't get an accurate reading
                         C    0.6 ohm

Bal :  Top : 1 (infinite)  - can't get an accurate reading
         Bottom:  0.6 ohm

Vol:  Top:  1 (infinite)  - can't get an accurate reading
        Bottom:  0.6 ohm

 I have tested the other ground areas and they measure 0.6ohm.

Thanks for your help as always....Dave

[Paul Birkeland]

Try measuring the other end of the black wire going to selector switch B.

-PB

[wullymc]

I measured from Selector B to top of Bal :  0.6ohm
From B to top of Vol:  0.6ohm
From top of Bal to top of Vol:  0.6ohm

[wullymc]

I went around and tested the grounds:

Power input E: 0.6ohm
Ground tab by D:  0.6ohm
Ground tab by C: 0.6 ohm
Ground tab by Bal: 0.6ohm

Both drain wires attaching to ground tab by Bal:  0.6ohm

R1 ground tab:  1 (infinite)
L1 ground tab:  1 (infinite)
R2 ground tab: 0.6ohm
L2 ground tab:  1 (infinite)
R3 ground tab: 1 (infinite)
L3 ground tab:  1(infinite)

Selector switch:

1-12 all solid colours:  1 (infinite) except orange read 0.6ohm (going to R2 ground tab which is also 0.6ohm)

I reflowed all RCA ground tabs as well as the Selector switch and no changes to the values.

I have tested the wires from the Selector switch to the RCA jack ground tabs from the terminals and all register 0.6ohms.

Any suggestions as to what to do next?.....Thanks  ...Dave

[Paul Birkeland]

R2 ground tab: 0.6ohm
L2 ground tab:  1 (infinite)

This is problematic.  Try the other 2 switch positions to see if the left channel ground tab is also infinite.

-PB

[Rocketman248]

I'm getting pretty much the same problem.  Did you get any resolution to this?