5F1 possible 5Y3 or socket problem

Jerry garrcia

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Hi. Did something stupid. Had nothing to do since I was waiting for some parts for a build.

I tore down my “Champ” and resoldered it all to get a better visual appearance.
When I started it all up the lamp and rectifying tube glowed like the star from the bible. Everything was silence and no 50Hz hum. The problem started when I plugged in the guitar since the amp was still silent…
All tubes glowed.
I measured the voltage at measuring point P1 (connection by C1, R13, T2 and Pin 8 from V3) and was around 0,356 VDC. More than a factor 1000 to low. Before my resoldering it was 376 VDC. P2 and P3 was of course also to low.

I measured up T1 and the VAC values was correct on both lines, yellow 5.1 VAC, Red 340 VAC and green 3,2 VAC so the Transformer seems ok.
Measured the voltage at pin 8 on V3 and in the red wire, by the connection to V3 to P1, corresponded to P1.
This made me to draw the conclusion that the problem is in ether the V3 socket or in the rectifier tube. Correct?
If so, is there a way to tell in which “component” the problem is? The whole amp has been demounted and rebuilt 3 times with the same components, except the wires to problem solving issues and “ugly appearance”.
Can the problem otherwise be downstream due to faulty components or grounding issues?

If anybody has the know how to narrow down the issue, don’t hesitate to reply even if it is my own fault for tampering with a functioning amp.
I have all the components “in stock” at home except for a 5Y3 tube and V2/V3 sockets.
I’ll include pictures.
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2L man

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Without tubes just measure rectifier socket voltages! If they are OK install only rectifier and you get DC if rectifier operates at least partially. There is a possibility that other diode has failed?

Did you have two AC voltages against Common/ground?

I recall that measuring over diodes, both silicon and tube which are series there, you should see AC when multimeter has voltage set to AC. And DC when MM is set to DC. If both wave diodes (tube+ silicon) show same voltages they all four also operate.

Silicon diodes are most sensitive component to break in tube amps :)
 
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Jerry garrcia

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Without tubes just measure rectifier socket voltages! If they are OK install only rectifier and you get DC if rectifier operates at least partially. There is a possibility that other diode has failed?

Did you have two AC voltages against Common/ground?

I recall that measuring over diodes, both silicon and tube which are series there, you should see AC when multimeter has voltage set to AC. And DC when MM is set to DC. If both wave diodes (tube+ silicon) show same voltages they all four also operate.

Silicon diodes are most sensitive component to break in tube amps :)
I just did the measurements on Rectifier socket without tube.
Ground is measured on transformer bolt in chassi.
Measurement between ground and chassi = 0.
Pin 1 = 1,6-2,8 VAC (unstable)
Pin 2 = 5,35 VAC
Pin 3 = 2,24-3,57 VAC (unstable)
Pin 4 diode = 87 VAC (dropping value while measuring)
Pin 5 = 333 VAC
Pin 6 diode = 78 VAC (dropping value while measuring)
Pin 7 = 333,5 VAC
Pin 8 OL ≈ 1,06 VAC (unstable)

Does that give any solution to where the problem is?
 

2L man

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There should already be DC after silicon diodes. If your multimeter has a diode measuring feature use it to test them. It produce about 1mA constant current and messures voltage and when Red probe is on SS diode anode and black on cathode it show about 0,5V which means diode is fine. However I think they have "burn" more likely than rectifier tube or transformer!

If your MM does not have that feature you can tack solder pieces of wires over SS diodes and test if tube rectifier operate.

If tube rectifier does not rectify and produce DC you can remove it and chance tack soldered wire pieces over tube diodes and test if SS diodes rectify.

If you think you will continue building amps, nest time you order components consider buing a SS rectifier kit which simulate tube rectifier. It consists a tube socket and a tube base and two SS diodes and sometimes two current limiter resistors which simulate higher voltage loss there comes to tube rectifier. There are ready made SS rectifiers fir tube socket but they can cost even ten times more.

Usually there don't come proper filament voltage values against the ground because often filaments are isolated from ground and direct heated rectifier tube filaments must be isolated because there come HV to them as well. So measure AC between pin 2 and 8.
 
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Jerry garrcia

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There should already be DC after silicon diodes. If your multimeter has a diode measuring feature use it to test them. It produce about 1mA constant current and messures voltage and when Red probe is on SS diode anode and black on cathode it show about 0,5V which means diode is fine. However I think they have "burn" more likely than rectifier tube or transformer!

If your MM does not have that feature you can tack solder pieces of wires over SS diodes and test if tube rectifier operate.

Usually there don't come proper filament voltage values against the ground because often filaments are isolated from ground and direct heated rectifier tube filaments must be isolated because there come HV to them as well. So measure AC between pin 2 and 8.
So I should:
1) Measure over the diode or change them to see if they work.
2) measure AC between pin 2 and 8.

If the diodes on rectifier sockets does not work, could it be the reason for not having the correct DCV at measuring point P1. From rectifier to C1?

On other thing. I just got shocked. Had a teams meeting and the amp was plugged in but turned of. I touched the wires White/brown on transformer and also chassi wit the same hand and got quite a shock. Could continue with the meeting. How could that be? No tube has been inserted
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2L man

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So I should:
1) Measure over the diode or change them to see if they work.
2) measure AC between pin 2 and 8.

If the diodes on rectifier sockets does not work, could it be the reason for not having the correct DCV at measuring point P1. From rectifier to C1?

On other thing. I just got shocked. Had a teams meeting and the amp was plugged in but turned of. I touched the wires White/brown on transformer and also chassi wit the same hand and got quite a shock. Could continue with the meeting. How could that be? No tube has been inserted
1. If your MM has diode measure option use it. If not replace them. When you do voltage measuring silicon and tube diodes should be seen as one diode!

2. When you see about 5VAC between pin 2 and 8 it is possible that 5Y3 warms as well. If soclet is OK and filament concucts.

If mains primary wires insulation leaks it is possible to get schocked touching them and chassis and that you MUST examine very well because that should not happen!!! But I am afraid there might leak current to chassis?

Using MM resistance setting test that it show about 100 ohms between mains cable blug hot and neutral when power switch is ON. If you did take PT resistance values before installing refer to them. Then change other probe to chassis and look that it show infinite or at least Mega ohm resistance. Test also between mains plug hot/neutral to mains safety earth contact. If not very high resistance you have a primary leak!!!

Turn Mains switch off and does resistance show infinite? Remove fuse? ...

Possible mains pilot light is my first quess. Then possible X-capacitor. Then transformer... of fuse or switch?
 
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andrewRneumann

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Please be careful.

You were probing around in an amp, with your fingers, while it was still plugged into the wall. Please unplug it or have some way to cut mains power before you get in there with fingers or a metal tool.

Amp building is fun, but not worth taking life altering risks for.

If you want to know what shocked you, it is a matter of tracing the schematic from mains live wire to the power switch. Everything between the mains live wire and power switch is a potential shock hazard when the amp is plugged in, and that is assuming everything is working correctly. Use your voltmeter probe (instead of your fingers) and see if you can find it.
 

Jerry garrcia

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Please be careful.

You were probing around in an amp, with your fingers, while it was still plugged into the wall. Please unplug it or have some way to cut mains power before you get in there with fingers or a metal tool.

Amp building is fun, but not worth taking life altering risks for.

If you want to know what shocked you, it is a matter of tracing the schematic from mains live wire to the power switch. Everything between the mains live wire and power switch is a potential shock hazard when the amp is plugged in, and that is assuming everything is working correctly. Use your voltmeter probe (instead of your fingers) and see if you can find it.
I know. The amp was turned of by the powerswitch for 30 min but still plugged in. The lamp turned of, no tubes had been connected for 18h so no DC should be in the system and since the pin 8 and therefore P1 only 18 h earlier only had 0,360 VDC I thought that there were no chance that the amp had any dangerous electricity in it.
The shock didn’t feel like 230V.
I was just playing around with my hand during the boring meeting over teams and fingering in the amp without thinking. Stupid still since it was plugged in.
Good thing that I found out a problem but bad that I did the resoldering of a functional amp. Something is wrong except the lack of power to P1 from pin 8 in V3. The voltage to V3 from the transformer is correct but the VDC output to C1 is 1000 times to low and and shocked by touching the connected white/brown wires from T1 and the chassi.
The only bad soldering joint I can see is by 230 VAC from transformer to the lamp. “Something is rotten in the state of Denmark “.
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Jerry garrcia

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I’m getting crazy. So now I have changed the diodes I’m rectifier sockets, resolderd the connections to the lamp, measured all PT output currents (same VAC as specs), reconnected and checked all connections to rectifier sockets and ground connections to groundbus and input ground. When I attach the red wire (that goes to C1) to pin 8 together with yellow the (no tube in) the voltage drops to 1,06).
Put in 5y3 tube and it heats up and glows but still just around 560 mVDC on the red wires attached connection on the board (connects with C1, red wire from T2, 2W resistor), and all measured points P1, P2, P3 shows voltage in mVDC.
All is the same as before I redid the whole thing except for new grounding to inputs jacks according to picture that I previously posted.

1) what could be the problem?
2) should I replace all components from C1 and forward?
3) tube socket problem?
4) tube problem?
5) put in ground wires to input jacks between J1 switch->chassi->J1 chassi?

I’m stuck.
 

2L man

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When there is no operative voltages, following schematic you just have to measure where the voltage gets lost!!!

I already have wrote that over rectifier diodes, which in your case consists two diodes, one silicon and one vacuum diode, multimeter show AC and DC voltage over them when they function. This is when they suppose to short current other direction and resist current other direction. I don't remember what are the DC and AC voltages but few hundred volts anyway. Buth both sides should produce about same AC and DC results.

So start AC mesures from Mains AC. Then measure both, AC and DC over rectifier. Then continue using DC measuring...
 

Jerry garrcia

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Jerry, did you find where the Voltage got lost?
Sorry but no. Haven’t had the possibility to do the measurements due to kids, work, dog, wife and other things that gets in the way for conducting fun and important stuff.
Will do tonight. Since the current is ok from the PT and the diodes are changed I thought that if I desolder the wire from pin 8 of V3 at the connection from the component board and measure the end towards the component board. It should be around 350 VDC if the problem is a short down stream. If not, the problem should be in the rectified socket or 5Y3 tube? Correct logic?
 

Jerry garrcia

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Just measured wire from V3 Pin 8 = 360 VDC. Seems like the problem is after the rectifier tube. Damn. Might be a short somewhere… just about a 100 more connections to check.
P1-3 129DCV so haif the voltage just missing. Resolder the reslsistors from light to groundbus. Resolder R1-3 and fuse.
 
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