wild resistance readings HELP

patm · 3361

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Offline patm

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on: April 22, 2011, 11:53:14 AM
Just finished kit and I get these resistance readings:
BH/ME
1 */*
2 */*
3 0/2.8 M ohms
4 */*
5 */*
6 2.4 K ohms/2.4 K ohms
7 2.9 K ohms/1.7 M ohms
8 0/3.0 M ohms
9 2.9 K ohms/3.0 M ohms
10 2.4 K ohms/2.4 K ohms
12 0/0
13 270 K ohms ^/.6 M ohms
14 0/0
20 0/0
22 0/2.0 M ohms
B3 2.9 K ohms/2.1 M ohms
B6 2.9 K ohms/2.1 M ohms
RCA R 90 to 100 K ohms/101 K ohms
      L 90 to 100 K ohms/3.4 M ohms
     Gnd 0/0

In the beginning there was nothing, then it blew up!

FP III, Paramount 300b (Takatsuki TA-300B), both with Mundorf S/O caps, Mikes iron, HFBG Eros,Oppo 103,Rega RP6 2m black ,Vaughn Triode JR II


Offline patm

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Reply #1 on: April 25, 2011, 03:02:42 AM
OK I didn't get any replies for my request for help, in reading my request, maybe it wasn't clear that I was asking for help. These resistance readings are so far from spec that I need help trouble shooting the problem. Thanks

Pat

In the beginning there was nothing, then it blew up!

FP III, Paramount 300b (Takatsuki TA-300B), both with Mundorf S/O caps, Mikes iron, HFBG Eros,Oppo 103,Rega RP6 2m black ,Vaughn Triode JR II


Offline Grainger49

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Reply #2 on: April 25, 2011, 03:22:21 AM
Pat, I promise to check this morning and get back to you.  

Ok it took to 1:20 PM.

The readings are purely out of whack on T3, T7, T8, T9, T13, T22, B3, B6 and the left RCA jack.

1) Quickly, the RCA jacks should "see" the 100k pot regardless of the pot setting.  It should read about 100k ohms.  Since the left doesn't, lift the wire going from the wiper of the input volume control to pin 2 or pin 7 of the 12AT7 and see what the pot reads.  (I'm not tracing this because you can easily find the left input RCA jack and the wiper of the pot, center lug.)

2) Terminal 3 should be grounded, it is screwed to the chassis plate.  Recheck that.  I can't imagine why it reads 2.8M ohms.

3) Terminal 7 has a 3k ohm 5W resistor to ground at, again, Terminal 3.  If Terminal three isn't grounded it will read odd.  Check from Terminal 7 to terminal 3, not the chassis.  You should read the 3k resistor.

4) Again, like Terminal 3, Terminal 8 is screwed to the chassis.  It should be grounded.  (this now makes me wonder where you clipped your meter's ground terminal to when reading.)  This might have given you odd readings depending on where you clipped the meter lead.  See 2) above.

5) Terminal 9 is a repeat of Terminal 7.  Measure from Terminal 9 to Terminal 3, not the chassis plate.  You should read the 3k ohm resistor.  See 3) above.

6) Terminal 13 is probably Ok.  It says climbing to 270k ohms.  This is the "Bleeder" resistor for the power supply to keep us from hurting ourselves if we touch a charged capacitor.  But the capacitor from Terminal 12 to Terminal 13 will make reading it hard.

7) Terminal 22, like Terminals 3 and 8, is screwed to the chassis.  This is the third one and reading the manual it says, "attach the negative lead... of a volt-ohm meter to ground," which leaves it open where to ground the meter.  It might be that a ground wire jumper has been left off.  Be certain that the IEC connector is grounded to the chassis ground lug and to Terminal 16.

8) And finally, B3 and B6 are connected to the cathodes of the output tube through the resistors mentioned above in 3) and 5).  If it reads high maybe the wire from B3 or B5 to Terminal 3 is not continuous (cold solder joint).  Or the problem in 2) above is the cause.

Hope this helps.

« Last Edit: April 26, 2011, 07:34:00 AM by Grainger49 »



Offline patm

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Reply #3 on: April 26, 2011, 08:13:44 AM
Granger,

Yes, someone else must have been posting as I posted my reply. I am working nights (1830 to 0630) this week so I will have about an hour a day to troubleshoot until Friday.

Pat

In the beginning there was nothing, then it blew up!

FP III, Paramount 300b (Takatsuki TA-300B), both with Mundorf S/O caps, Mikes iron, HFBG Eros,Oppo 103,Rega RP6 2m black ,Vaughn Triode JR II


Offline patm

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Reply #4 on: April 26, 2011, 09:05:12 AM
Granger,

Progress, Tracing the ground circuit from rca gnd to pot to term 3. Its all good (0 ohms) until I get to 3L. I wiggled that connection and now get proper resistance readings everywhere (with blk lead on rca gnd). My brother who actually built the kit (his first) is rewetting 3L (after some disassembly) I will post back with the results.

Thanks for the help so far.

Pat

In the beginning there was nothing, then it blew up!

FP III, Paramount 300b (Takatsuki TA-300B), both with Mundorf S/O caps, Mikes iron, HFBG Eros,Oppo 103,Rega RP6 2m black ,Vaughn Triode JR II


Offline patm

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Reply #5 on: April 26, 2011, 10:00:53 AM
Success!

After rewetting 3L and a loose connection at the hf jack (blk wire from t12) voltages are all within 15 percent. My brother is smiling from ear to ear and is listening as we speak. Thanks once again Granger.

Pat

In the beginning there was nothing, then it blew up!

FP III, Paramount 300b (Takatsuki TA-300B), both with Mundorf S/O caps, Mikes iron, HFBG Eros,Oppo 103,Rega RP6 2m black ,Vaughn Triode JR II


Offline Grainger49

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Reply #6 on: April 26, 2011, 12:24:30 PM
Glad to the him to smile!