Paramount voltage concerns **SOLVED!!**

[wullymc]

I have gone onto Voltages  (300B)

Right Monoblock:

OA voltage stays at 351 

Because the OA stayed high on the Right one I didn't proceed to do any more voltage checks.


Left Monoblock

OA goes down to 296. 

I have a problem with OB.  I register a 0 and even if I adjust the potentimeter it stays at 0.

Terminal      Measured Voltage    Manual
1                      447                        440
5                      71                            71
9                        0                          200
10                      0                              0

16                    463                        457
17                        0                              0
18                        0                              0
19                        0                          200

A1                    74                            74.1
A2                    440                          440
A3                        0                          close to 0
A4                      69                            69.2

6V Red              2.6                          3.1
6V Black            2.6                          3.1

Kreg A side          0                            4.1
Kreg B side      16.3                          6.3
OA                    298                        300
OB                        0                        200

Kind of stuck as to where to go from here.

For R Block - problem with OA staying at 350=351

L Block major concerns:  OB, 9, 19, Kreg both A and B sides.

Any suggestions.  Thanks....Dave
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[wullymc]

I have tried swapping the 5670 tubes to see if the OA voltage would be better in the Right Monoblock. 

It still reads 350V and doesn't fall below after 20 seconds.  The manual says to check your wiring.  I will have to try to figure out why this would be.

If anyone has any suggestions to my 1st post or this I would appreciate the help.

Thanks...Dave

 

[marantzfan]

Perhaps if you posted some pictures of the underside of the amp it would assist others in helping you through the troubleshooting.

 

[wullymc]

Thank you.  I will post some pictures this weekend of the underside.

All LEDs are lit for both Monoblocks.  When I have time I will reflow all solder joints to see if this rectifies the problem.

I have checked older posts for these problems that I am having.  With the OA not going down 1 person had a 5687 tube in there instead of a 5670 tube.  That is why I swapped tubes.  The voltage stayed the same. As for the 0 voltage at OB I am checking R3, R4, 431 chip and -reg A and kreg A.  I will reflow all these and look at the connections to the tube socket.

I guess my not knowing is where/what provides the voltage to OA for the one that doesn't go down from 351?  In the voltage check it just states shut off and recheck wiring.  What I would like to know is where to look for the problem.   

 

[Paul Joppa]

Right monobloc - OA at 350v. =====================

OA feeds the regulator side of the 5670, specifically OA to plate (pin B6); the cathode (B8) goes through the 431 at kreg(B). Yes this is confusing, swapping sides - pay attention!

The regulator is protected by the Zener string which is why you see 350v. This indicates that OA is in fact feeding current to the Zeners, and thus the A side C4S (the portion near the center, with the LEDs and two transistors) is working.

Without a measurement of the kreg(B) voltage it's hard to know why the regulator triode is not drawing any current. You can check the cathode  and plate connections. Since all LEDs are glowing, I infer that the regulator bias string is intact - that's the two 149K resistors R2(B) and R4(B) and the 2.49K regulator reference resistor R3(B). You might make sure the 431 on the B side is correctly oriented and properly soldered.

If the above does not turn up anything, measure the voltages at kreg(B) and both ends of the resistor R3(B)

Left monobloc OB = 0 ==============================

OB goes to the driver triode plate, B4. Since the cathode of the driver, B2 and kreg(A) is also zero, I suspect the plate-OB connection. The most common cause is a poor solder joint at the collector (middle pin) of the MJE-5731A transistor. This pin is connected to the heat sink on the transistor, making it more difficult to get the pin hot enough for a good solder joint.

 

[wullymc]

Thank you sooooo much Paul. 

You don't know how much I appreciate your input.

This is exactly what I wanted to hear.  Now I know where to go!!   I will probably tomorrow take the time to verify and resolder the areas that you have indicated.  I will also take readings at kreg(B) and both ends of R3(B).

Fingers crossed!

Take care...Dave

 

[wullymc]

Paul,

You sir are a genius!!!  L Block is good now.  I resoldered B4 and now I get the following:

OB          175
9            175
19          175
Kreg A    3
Kreg B    7

Thank you thank  you thank you.

Tomorrow I will work on the R Block.  Hopefully I will get that up and running!

Take care....Dave

 

[wullymc]

Couldn't wait to do the other Monoblock.

Resoldered B6, B7, & B8.  Checked voltages and everything works!!! Woo Hoo!


I wasn't able to get a shorting jack that I made to work so I haven't yet adjusted the hum pot.  I am going to hook it up and see how it sounds.....exciting.

Thanks again for the assistance.  Much much appreciated.

Listening now on cheap speakers to start...just incase.  Sounds really good.  Tomorrow I will hook them up to my Horns.  Currently being lead by a Quickie!.....

Super happy.  Thanks again! 


Darn it.  Left Monoblock lost music after 30 minutes.  WIll look into the voltages tomorrow on that one.  Good night!

 

[wullymc]

Well this morning I retook the voltages. 

Everything was ok.

I plugged up the Paramounts to my good speakers.  I heard hum on both speakers so I adjusted the hum pots.  I thought this was encouraging to hear hum on the bad Paramount.  Unfortunately, when I played music no sound came out the bad paramount.

I swapped Tubes and still no sound.  I resoldered all the connections on the OT-1 and binding posts and made sure the wiring was correct.  No sound.

I saw Doc's post to thdewitt "

The next step is to take PB's advice to put a signal into the amp and trace it. You can check it at the center pin of the RCA, then measure AC voltage right at pin 3 of the 5670. If they aren't the same maybe the 220 ohm grid stopper resistor at pin 3 is damaged.

If they are the same, measure AC voltage at pin 3 of the big tube. It should be a lot bigger because the first tube will have amplified it. If it is not, once again make sure the 220 ohm grid stopper resistor at the pin is good. If signal is good all the way to that point, measure it at output transformer OT-1 terminal 7. Again, it should be a much higher voltage. If you don't see signal there check your output cap connections. If signal is good there, go over your output transformer secondary wiring and the binding posts."

Unfortunately, I don't get AC voltage using my meter at either Paramounts for the centerpin of RCA, B3, A3, or Terminal 7.  It reads 0.

I have used multiple sources, computer through DAC and Record.    The last time I looked at the bad Paramount the B side LED were not lighting up.  I will go come back either tonight or tomorrow and post some voltages.  I think I will also resolder B3.

Take care...Dave

 

[Grainger49]

Did you try the good interconnect feeding the "bad" amp?  Just want to be sure you are getting a good signal to it.

 

[wullymc]

Thanks Grainger.

I tried the other interconnect and still no sound.  I just resolders B3 and the RCa jack.

Turned on the amp and all 4 LEDs were lit and I got 296 on OA and 442 on A2.  But when I went to OB it was at 89V.  I went to adjust it and then noticed that OB was 0 and the 2 LEDs on the B side were not lit. 
Now I was getting 0 for 0A and on Kreg B. 

I resoldered B6, B7, B8, &B4.

I restarted the Paramount and again all 4 LEDs were lit and I got 296 on OA and 442 on A2.  But when I went to OB it was at 89V.  I went to adjust it and then noticed that OB was 0 and the 2 LEDs on the B side were not lit. 
Now I was getting 0 for 0A and on Kreg B and both sides of R3 (B).    I think I might call it a day.

I feel like I am so close but yet so far!....Dave

 

[fullheadofnothing]

Unfortunately, I don't get AC voltage using my meter at either Paramounts for the centerpin of RCA, B3, A3, or Terminal 7.  It reads 0.

Have you checked to make sure your jack isn't shorted? Measure the resistance between center pin and ground.

What signal are you feeding it? Is it a 60Hz sine wave? Some meters cannot read much in the way of AC that isn't the mains frequency they expect. If you haven't already, download a 60Hz sine to your computer or phone and use that as your signal. If you're still not getting a reading at the jack you may need to turn up the level on your source.

 

[wullymc]

Thanks for the input Joshua,

I tried the AC for both Paramounts (one of them works fine)  I did the 60Hz sine wave from my Computer & phone.  I hooked up the Paramount to my Phonopre/Quickie and played a record.  All were a no go.

Dave

 

[fullheadofnothing]

What is the resistance between hot and ground on the RCA?

 

[wullymc]

I have tested both Paramounts and both resistances indicate 1.

Dave

 

[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.