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PT Help.

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Good Day everyone.
It has been awhile.

Ill get right into it.... I have an sse, the Pt is an edcore xwpr035-120
Primary 115 60hz
Sec. red/red 740v@200ma
Brown/brown 6.3v @ 5a (measured @7v)
yel/yel 5v @2a

The pcb has been tested using a different pt( 6k7vg) from Hammond, and the board worked quite well. Great sound, and loud.
after installing in new chassis with edcore Pt xwpr035-120,opt(cxse25-8-5k,and choke.

Ive no amplification??
volume pot is an alps 100k, and have to turn full to hear anything from spekers.
short of replacing PT with the Hammond, is there something else I can try?
some measurements below:

12at7 pins 4 and 9 measured 6.8-6.9v
rectifier tube(5au4) measured approx. 454v/
at choke connection 454v measured too.
across coupling caps, 454v left ch 99v at right channel. ( though upon inspection I may have right ch cap reversed)
driver tubes are 6l6
All tubes glow, though seem to run a little hotter then when used with 6k7vg


Thank you to all who reply
 
Good Day everyone.
It has been awhile.


The pcb has been tested using a different pt( 6k7vg) from Hammond, and the board worked quite well. Great sound, and loud.
after installing in new chassis with edcore Pt xwpr035-120,opt(cxse25-8-5k,and choke.

Ive no amplification??
volume pot is an alps 100k, and have to turn full to hear anything from spekers.
short of replacing PT with the Hammond, is there something else I can try?
some measurements below:

Thank you to all who reply

It may be some kind of connection problem, maybe your input connection as suggested by W5JAG.
Also check all your grounding connections.

You say it worked fine when you had it bread boarded with the Hammond transformer but after you
assembled it in your chassis with the Edcor transformer you're getting the problem with no sound
output. This is why I suspect it is a connection problem.

If you cannot get it to work while assembled in the chassis, I know this would a major PITA but
disassemble it and bread board it again with the Hammond transformer then switch in the Edcor.
If it is okay then it is some kind of connection problem when assembled in the chassis.

I have the Edcor XPWR035 in my high voltage SSE and its ben working fine for 5 years.
 
If the board was tested with am Allied 6K7VG and it worked, the board had been shown to work, so therefore, unless you have changed something, it was assembled correctly.

I am assuming that you mounted it in a chassis using the same OPT's, (or different OPT's?), but a different power transformer, and it doesn't work now.

Your voltage readings confirm that the power transformer is doing it's job. It can not be responsible for very low output. It and any external power supply (choke of aux cap) connections are properly wired.

If the board, transformers and other parts were assembled into a chassis and then the low output was discovered, the issue is likely with the wiring to the OPT's or input connectors.

The possible errors on the OPT wiring is a missing jumper or UL connection to the middle screw on the OPT primary connection, A ground wire connected to the wrong screw on the secondary connections. Speaker terminals that are not isolated from the metal chassis (both terminals shorted to the grounded metal chassis).

You should have a reading of over 400 volts on all three of each screws on the primary side of each OPT, and zero on each of the two secondary screws (negative meter lead on ground).

The usual culprit on the input side is a miswired volume pot, or reversed connections from the input connections to the pot or board.

across coupling caps, 454v left ch 99v at right channel. ( though upon inspection I may have right ch cap reversed)

This reading isn't right. Measured to ground there should be from 100 to 200 volts on one end of each coupling cap, and zero volts on the other. Either way both channels should be similar (not necessarily identical).
 
I wired up the PCB as I had before minus the volume pot. A direct input to PCB.

Readings.
Red/red 386 to 404
Yel/yel 5.3 to 6.4 DC. 470ac
Opt 464 /448
Pin 9 12at7 3.3 to 7dcv
Coupling caps 265/256 right side
97/446 left
For general knowledge the opt's are cxse25_8_5k

Going to change coupling caps and the 5w bias resistor Incase one or more have gone bad. With all the testing.
Also going back to 5ar4 rectifie. Though the Hammond can drive the 5u4gt with ease and it as a lower Ma DC than the edcor.
Will get back as time permit.
Thanks everyone. Frustrated I am, when I know the board will work.
 
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It would help if you could post a picture of the board and the way you have it currently wired up. That way it's easier for me to see which parts you have and how to probe them. For now I will use component numbers and terminal connections.

Wild card (this has happened exactly once and could not be fixed remotely, the user had to send me his dead board, which I fixed in one minute after seeing it). A really good picture could have found it. Have you drilled out any of the holes in the board to accommodate parts with fat leads like boutique coupling caps?

I would hold off on changing the coupling caps. I also doubt that they are your main issue for now. It is possible that you have two problems. Let's figure that out before changing any parts, since that has a low probability of finding the problem, and may create another one.

You state that you are getting very low volume. Does this apply to both channels, or just one? Is the low volume sound clean, or distorted? Does the sound from both channels appear equal in volume and distortion. Does sound come from one or both speakers when signal is applied to only one input? Try each input separately.

Your voltage readings show a big difference between the two channels. Either I'm not interpreting what you are showing correctly, or one channel is completely dead from a DC voltage perspective. Lets fix that first.

Can you take several voltage readings with the negative voltmeter on a good PC board ground point, and the meter set to DC volts? A good ground is the end of R17 near the center of the board (R17 is one of the 5 watt cathode resistors). The input connector ground or the power transformer "T1-RED-YEL" terminals are also good.

Make the following measurements, with all tubes installed and warmed up for a minute or so. :

Test the power supply:

Each end of R1 or the L1 connector. R1 is the 5 watt resistor in the power supply.

If you have over 400 volts DC on each end of this resistor, the power supply is working properly. AC voltage readings are not needed if this is correct. There should be different numbers on each end. The end toward the rear of the board will be lower, and the difference will tell us how much current is flowing through the board.

Test the output stages:

Each of the 3 screws on the primary side of the OPT. These readings should all be within a few volts of each other, and roughly the same between each channel. Your readings show a channel / channel difference.

Each end of the other 5 watt resistors, R17 and R27, yes one side is grounded, and should have 0 volts, I'm just covering all the bases to determine if one of the tube sections isn't working. The readings on the ends closest to the output tubes will tell us if each output tube is working, and how much current is flowing through them. 30 to 40 volts DC are normal.

Test the input stages:

Each end of the 10K 2 watt resistors feeding the CCS chips, R14 and R24.

Each end of the coupling caps C11 and C21. This is where things are wrong in your posted readings, but I'm not sure how you made them. If they are done in this manner something is wrong. One end of each cap should have nearly zero volts, and the other should have about 100 to 200 volts. A 400 volt or so reading indicates that one side of the 12AT7 is not working.

The DC voltage at the end of R10 and R20 furthest from the board edge. These are the resistors closes to the small electrolytic caps on either side if the input connector. There should only be a few volts here, usually about 1 volt.

Note, I will be leaving on a road trip early Wednesday morning, returning the following Monday. (Orlando Hamfest). I will not have reliable internet access during that time, only phone connection.
 
Grrr

After some investigation,I found a bad resistor,replaced it.
Installed new bias resistor s, and coupling caps.
Double checked rest of PCB.
Checked out good (values in correct places)

Readings have not changed.
Rectifier b+488 b- 186 5ar4 sovtek
12at7 pin 9 - 30vdc
Pin 1 feeding right ch 256vdc

Coupling cap
Right 256vdc/0
Left 85vdc/0

6l6 drivers 480vdc
Bias resistor both 39vdc
Have look at photo, wired correctly.

I have clearly missed something.
 

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It is hard to tell but I'm looking at your input wires from the vol pot to the board, are the red wires the signal wires (wiper wires from the pot) ?
If they are then it appears they are connected to the ground terminals on the board. The terminals for the signal wires are the two outer terminals.
 
Top side

Here is top side showing most resistors, I've triple checked placement and values, all are correct.
No more signs of discoloration .Used a magnifying glass go check solder and for cracks, nothing bad there.
I did find that the speaker output Jack's were grounded to the chassis, drill holes were just large enough to allow post to squeeze thru.
Chassis was not built by me.... I have enlarged the holes. Maybe that was issue?
 

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I did find that the speaker output Jack's were grounded to the chassis, drill holes were just large enough to allow post to squeeze thru.
Chassis was not built by me.... I have enlarged the holes. Maybe that was issue?

If all 4 jacks were touching metal that will cause your exact symptoms. It has happened to a few builders, and was one of the things that I suggested checking initially.

Speaker terminals that are not isolated from the metal chassis (both terminals shorted to the grounded metal chassis).
 
Test

George, Hope you had fun.

Following your test guide this is what I found. Put all back together

L1 connector.........493/481vdc

Opt primary........ L t..481/479/475
Rt. 480/478/475

R17...39.5 R27......39.8

R14.....385/480
R24.....444/480


Coupling caps
Rt.......5v/84
Lt........0/210

R10...... 2v
Checking the 12at7 pin 9 30vdc
8 0v,70v,6 88v,5 30v,4 30v,3 0v,2 0v,1 210v
Bad tube?

I have also fixed the speaker terminal issue. Now the only part grounded to chassis is a star gnd for safety and the input RCA
 
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