Paramount voltage concerns **SOLVED!!**

[fullheadofnothing]

Well, that ain't right. They should measure ~250KΩ. Either your meter can't read that high and 1 is how it shows "over limit," or it's reading 1Ω because it's shorted and your meter leads are close to 1Ω.

[Paul Birkeland]

You can also measure the AC voltage at the interconnect unplugged from your amplifier.  From your phone, you should see something like 200mV-1V. 

-PB

[wullymc]

Well, that ain't right. They should measure ~250KΩ. Either your meter can't read that high and 1 is how it shows "over limit," or it's reading 1Ω because it's shorted and your meter leads are close to 1Ω.

Hi Joshua,

Sorry you are absolutely right.  It measures 246K for me.


I still can't get any AC voltage check from the interconnect.  I have tried the 3.5mm to RCA cable from my phone and also the Interconnect coming from my Quickie that has my phono preamp/TT connected to it.  I don't know why.  I was able to use my DMM to get the AC for the 6V points on the big pcb in the Paramounts.  Confused.

...initially it played a good 30 minutes of music before it failed.

   Now when I take the voltages  OB is at 89 with all LEDS lit and when I try to adjust the potimeter it goes to 0 2 leds on B side go off and Kreg B is 0.
 

[wullymc]

Thanks for your patience with me guys.  I appreciate it.

I resoldered the middle joint to the MJE-5731A along with redoing B1, and 20L (that attaches to B3).


I have retaken the voltages and everything is fine now.  I have been monitoring OB for 5 minutes and it is steady and all 4 LEDs are lit.  Now I have just looked after 10 minutes and the reading on OB is now 38 and I get 0 for OA.   It is good initially then drops off. 

Do you have any ideas what could make OB fade like that? Where should I look?

Thanks....Dave

[Paul Joppa]

Most likely a bad solder joint is failing when things heat up. See my previous post for some places to look and data to take.

Since this is possibly the second bad solder joint, you may want to re-flow all the solder joints on the PC board just to be sure, and to avoid diagnosing more of them one at a time. Remember, the soldering iron heats the terminals and wires; the terminals and wires melt the solder.

[Doc B.]

This is something that I try to convey with only moderate success. On average it is faster to reheat all the solder joints in an area of the amp where you are having a problem than by poking around and then reheating what you think might be the problem spot.

[wullymc]

Thanks guys for the help.

Tomorrow (I hope) I will take off the pcb and resolder/flow all the points.  At that point I will also take some pictures with my camera and upload them here.  Hopefully this will solve all the issues with this one.  When I was listening for the 30 minutes when both were working I was amazed at the resolution.  Really exciting.  Just can't wait to get this one going again.

If all else fails I will send this one to you for assistance.

Take care.  Thanks again for the support, encouragement, and patience!  I really appreciate it.....Dave

[Paul Joppa]

Patience is the key - diagnosis and treatment is sometimes painfully slow by forum posts, but we nearly always get there! Once you do get it stable, wait for the break-in; it will take 20-50 hours of music before the capacitors and transformers are sounding right.

[wullymc]

Thanks Paul.

I couldn't wait until tomorrow.  Kids are asleep!

I took off the pcb and resoldered all connections.  Soldered the pcb to the correct locations..on the B terminals and 16 & 17.

Did my resistance checks:
         
         reading           Manual
-----------------------------------
1       infinity               *
5          999               1K
6        1115              1118
7          247K              249K
9       infinity              124K *
10          0                    0

11     infinity               3.0M
12     infinity               5.6M
13          0                     0     
14     infinity               9.2M
15     infinity               15M
16      increasing          *
17         0                      0
18         0                      0
19       infinity             128K *
20        247K              249K

A1        1013              1027
A2      infinity                 *
A3        247K               249K
A4        1013               1028

B1          0                    0
B2         7.96K              8.2K
B3         247K              249K
B4         296K              130k *
B5           0                     0
B6         349K              177K  *
B7         235                220
B8        1188K               *
B9           0                    *


Voltage checks:

OA          0 - 3              296
A2          447              440
OB            0                175

1            446              440
5              71                71
9               0               175
10             0                  0

16           468             457
17              0                  0
18              0                  0
19             0                175

A1           73                74.1
A2         442               440
A3             0                   0
A4           68                 69.2

6V red     2.6                3.1
6V black  2.6                3.1

Kreg (A)    0                 4.1
Kreg (B)    0                 6.3
OA            0                300
OB            0                175

Darn it.  No voltage now at OA!       Both LEDS on the A side lite up the B side LEDS do not lite up.

I am attaching some photos showing the resoldering and the steps to connect the pcb to B2, B4, B6, B8, 16U, 17U.

Any suggestions for getting OA back working?

Thanks again for your help....Take care...Dave

[wullymc]

I found this post from PJ for a person that was having 100V at OA:

"If the B side LEDs are not lit up, then there is no current running through them. From the diagram, you can see that the 100v you have goes through the LEDs, then 149K R2(B), then through 149K R2(B), then 2.49K R3(B) to ground. One of those connections is broken, presumably - or else the LEDs are in backwards.

It's the voltage dropped across the 2.49K resistor R3(B) that sets the shunt regulator voltage, so there's no surprise that voltage is not correct. It's possible (for example) that an error on this chain could damage the B-side 431 and short it, which would lead to about 100v on the shunt reg triode.

You can check the voltages on the varios resistors mentioned above, and on the 5670 pins 6, 7, and 8. This should give us more clues."

I have taken the voltages and am getting 0s across the board.  Unless anyone has any suggestions... I think I am done.  I have tried my hardest & done what research I can try to get this going.  I don't know what else to do.  I need someone to take this off my hands.

Its hard to take from listening to it for 30minutes and then feeling so far away from getting it to work.  I was ready to buy a Beepre to pair this with but if I look at the photo it looks about 10 times harder.

If it is okay I think I am ready to send it in for professional assistance. 
Take care...Dave

[Paul Birkeland]

0V at OA would suggest that either the center leg of the MJE5731A isn't well enough soldered, or that two adjacent pads on the PC board got soldered together by accident when you went back to reheat the joints.

It's also entirely possible that one of the wires going to the board itself is a little loose, particularly the ground wire that would feed BA/BB.

-PB

[wullymc]

Thanks PB,

Tried what you recommended.  Same result.    I would like to send it to you.


Thanks....Dave

[wullymc]

hi,

I took off the pcb again and warmed up the solder joints.


I am ready to reattach it to the Paramount.  I am attaching pictures if anyone can see any problems. 

Is there any way to test voltages without attaching it (ie. use a battery?).  Probably not but wanted to ask.

I have used my meter to check continuity and everything seems ok.  Does continuity indicate a good solder joint if you are measuring between the 2 solder joints (not the wires)?

Here are the pictures.    Really want to try to get this to work without sending it in but will if necessary.


Thanks...Dave

[Paul Birkeland]

Is there any way to test voltages without attaching it (ie. use a battery?). 

I have used my meter to check continuity and everything seems ok.  Does continuity indicate a good solder joint if you are measuring between the 2 solder joints (not the wires)?

Here are the pictures.    Really want to try to get this to work without sending it in but will if necessary.

The battery voltages would have to be pretty high to get the board to function, and you would have to simulate loads with large resistors, so it ends up getting complicated.

Other than some of the leads poking out on the bottom of the board being a bit long, it looks like that board should work well. 

Do also bear in mind that a loose wire going from the board to the terminal strips/tube socket could cause your issue.

-PB

[wullymc]

Thanks PB!

Well I reheated everything on the pcb and resoldered a couple of connections.  i reattached everything to the Paramount.

Took voltages and everything is good!  YAY!!!!

Waited 20 minutes, connected speakers and I have sweet music!!  YAY!  I listened for 1 hour.

Thanks again for your posts, without you and Paul Joppa's suggestions I would have been really stuck.

The only thing is when I power on the amp I get a "FFFFFFFFFFFFFFFF" sound for about 1 second.  After it is fine and there is no problems afterwards.  Do you have any idea what this could be?

Thanks again!...Dave