Studiomaster Valve Leadmaster violated!!
- Thread starter Dreadneck
- Start date
GoldenVulture
Braindeadologist
Re: Studiomaster Valve Leadmaster violated!!
The diodes to the right are mounted correctly. The other ones appear to be but they're a bit unclear. All the caps are mounted correctly.
The only other thing is the four caps to the left. They're all 47uf on that board. The circuit says the three to the right end of that four should be 33uf.
The diodes to the right are mounted correctly. The other ones appear to be but they're a bit unclear. All the caps are mounted correctly.
The only other thing is the four caps to the left. They're all 47uf on that board. The circuit says the three to the right end of that four should be 33uf.
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Re: Studiomaster Valve Leadmaster violated!!
Yes, I don't know why he chose to put a 47uf there. I did the same first because I followed his pictures, but when I got hold of the schematics I switched it to 33uf.
But then I know that I installed the diodes correctly. Then I guess that eihter the resistors or the large filtercaps is the problem. I replaced the old resistors so that should be good now, but the caps are still 50V below specs.. I've ordered new ones so I hope that will do it.
Do you have any other ideas?
Yes, I don't know why he chose to put a 47uf there. I did the same first because I followed his pictures, but when I got hold of the schematics I switched it to 33uf.
But then I know that I installed the diodes correctly. Then I guess that eihter the resistors or the large filtercaps is the problem. I replaced the old resistors so that should be good now, but the caps are still 50V below specs.. I've ordered new ones so I hope that will do it.
Do you have any other ideas?
GoldenVulture
Braindeadologist
Re: Studiomaster Valve Leadmaster violated!!
Re: Studiomaster Valve Leadmaster violated!!
So now I've finally checked. I get 485 VDC.
I also managed to fix the issues at the power stage.
Now smoke is comming up from behind the preamp tube board. I can not se exactly what is smoking, but it almost looks like it comes from the 4th preamp tube socket. That is, between the board and the socket. So it is very hard to see.
So now I've finally checked. I get 485 VDC.
I also managed to fix the issues at the power stage.
Now smoke is comming up from behind the preamp tube board. I can not se exactly what is smoking, but it almost looks like it comes from the 4th preamp tube socket. That is, between the board and the socket. So it is very hard to see.
GoldenVulture
Braindeadologist
Re: Studiomaster Valve Leadmaster violated!!
V4 is your Phase Inverter which splits the signal to the output tubes
So you connected the HT [ fuse and standby switch ] and fired it up ? With or without valves ?
Connected to the valve heater tap are some diodes ,led's and a fan which turns on with the stand by switch. Red led /standby off Green led /standby on. Is this section working ?
You're probably going to have to get under that board and find out what has smoked/burnt out.
V4 is your Phase Inverter which splits the signal to the output tubes
So you connected the HT [ fuse and standby switch ] and fired it up ? With or without valves ?
Connected to the valve heater tap are some diodes ,led's and a fan which turns on with the stand by switch. Red led /standby off Green led /standby on. Is this section working ?
You're probably going to have to get under that board and find out what has smoked/burnt out.
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Re: Studiomaster Valve Leadmaster violated!!
I managed to find the source, it was a resistor that burned.
So I replace it and no smoke.
Now, without any tubes at all it seems to work fine. But when I put tubes in the lamp I have between the amp and the wall starts to glow bright! Indicating a short or that something is drawing to much current.
The section with the leds work fine!
I managed to find the source, it was a resistor that burned.
So I replace it and no smoke.
Now, without any tubes at all it seems to work fine. But when I put tubes in the lamp I have between the amp and the wall starts to glow bright! Indicating a short or that something is drawing to much current.
The section with the leds work fine!
GoldenVulture
Braindeadologist
Re: Studiomaster Valve Leadmaster violated!!
Which resistor was it ? [ PS: you keep getting ahead of yourself here by plugging the valves in. I'm still trying to get you to test and verify the rest of the circuit before doing that.]:smokin:
On this board you should be able to test the HT feeds to the different valves.
In the schematic they are V1[484v], V2[424v], V3[349v] and V4[317v] and are right to left looking at the board. Still without valves,turn it on and test from the positive of each of those caps.
They may not be exact but hopefully in the ballpark of what I've listed here. If not it would suggest a problem on a particular feed.
Also don't presume they are feeding individual valves, they're not. V3 feeds valves 2 and 3. V2 feeds valve 4 . V1 feeds the reverb drive and the power tubes. [ as well as HT ] and V4 feeds valve 1
Which resistor was it ? [ PS: you keep getting ahead of yourself here by plugging the valves in. I'm still trying to get you to test and verify the rest of the circuit before doing that.]:smokin:
In the schematic they are V1[484v], V2[424v], V3[349v] and V4[317v] and are right to left looking at the board. Still without valves,turn it on and test from the positive of each of those caps.
They may not be exact but hopefully in the ballpark of what I've listed here. If not it would suggest a problem on a particular feed.
Also don't presume they are feeding individual valves, they're not. V3 feeds valves 2 and 3. V2 feeds valve 4 . V1 feeds the reverb drive and the power tubes. [ as well as HT ] and V4 feeds valve 1
GoldenVulture
Braindeadologist
Re: Studiomaster Valve Leadmaster violated!!
If all that tests good go to your power tube sockets.
pin 3 is your plate and is fed by HT via the OT so should be 485v. Pin 4 is fed by V1 via a 470 Ohm resistor [ on each valve ] and should be a little under 484v.
You could also test the other valves sockets for their high tension feed at this point ]
They're all 12AX7's so pins 1 and 6 are the relevant ones. The schematic tells you what each valve should be [ they vary ]
[once you get to the power tubes being in , make sure you have a speaker connected ]
If it's all good , put in the power tubes and connect a speaker and turn it on but don't turn on the standby.[ if you can connect your multimeter to read the HT voltage when you turn it on, do it so you can read if it is firing up properly ] If all is good / no light glow or odd reading on the HT, turn on standby and see if it remains the same.
if all is good Repeat the process by putting in valve4 [ Phase inverter ] then Valve 3 and then valve 2 and then 1.
If all that tests good go to your power tube sockets.
You could also test the other valves sockets for their high tension feed at this point ]
They're all 12AX7's so pins 1 and 6 are the relevant ones. The schematic tells you what each valve should be [ they vary ]
[once you get to the power tubes being in , make sure you have a speaker connected ]
If it's all good , put in the power tubes and connect a speaker and turn it on but don't turn on the standby.[ if you can connect your multimeter to read the HT voltage when you turn it on, do it so you can read if it is firing up properly ] If all is good / no light glow or odd reading on the HT, turn on standby and see if it remains the same.
if all is good Repeat the process by putting in valve4 [ Phase inverter ] then Valve 3 and then valve 2 and then 1.
Re: Studiomaster Valve Leadmaster violated!!
I've meashured the voltages and they came of wild..
So:
V1 = 480VDC
V2 = 477
V3 = 473
V4 = 474
This is a major difference. That could explain the smoked resistor. Oh it was without any valves.
The HT is at 485 as it should...
I meashured the choke aswell, it was about 908VAC
I don't know what's normal here though.
BTW I use a variac, I set it to 230Vac egen though the amp is set to 240. I live in Sweden and we have 230 in the wall so I figure that it would'nt get more than that anyway.
It must be better to have the amp expect 240VAC and give it 230 rather than put it to 220VAC and give it 230 right?
Which resistor was it ? [ PS: you keep getting ahead of yourself here by plugging the valves in. I'm still trying to get you to test and verify the rest of the circuit before doing that.]:smokin:
On this board you should be able to test the HT feeds to the different valves.
In the schematic they are V1[484v], V2[424v], V3[349v] and V4[317v] and are right to left looking at the board. Still without valves,turn it on and test from the positive of each of those caps.
They may not be exact but hopefully in the ballpark of what I've listed here. If not it would suggest a problem on a particular feed.
Also don't presume they are feeding individual valves, they're not. V3 feeds valves 2 and 3. V2 feeds valve 4 . V1 feeds the reverb drive and the power tubes. [ as well as HT ] and V4 feeds valve 1
I've meashured the voltages and they came of wild..
So:
V1 = 480VDC
V2 = 477
V3 = 473
V4 = 474
This is a major difference. That could explain the smoked resistor. Oh it was without any valves.
The HT is at 485 as it should...
I meashured the choke aswell, it was about 908VAC
I don't know what's normal here though.
BTW I use a variac, I set it to 230Vac egen though the amp is set to 240. I live in Sweden and we have 230 in the wall so I figure that it would'nt get more than that anyway.
It must be better to have the amp expect 240VAC and give it 230 rather than put it to 220VAC and give it 230 right?
GoldenVulture
Braindeadologist
Re: Studiomaster Valve Leadmaster violated!!
Ok. V2,V3 and V4 might not respond properly until their under load [ Valves plugged in]. Did you get as far as plugging in the output tubes ?
Maybe try putting in the output tubes then the phase inverter [Valve 4] and then measure V2.[ presuming everything seems alright when you put in the valves ]
I don't know how you got to this but there's no sense in measuring it for AC voltage. It sits between the HT feed and the V1 feed.
Your HT voltage is correct and after passing through the choke, your reading of V1 is 5 volts under the HT. The schematic says it should only be 1 volt difference. At the moment I wouldn't worry about that slight difference. It may change once the other feeds are under load.
Our Power system Down Under [ Aus ] is in the same area as yours . It varies from state to state. 230v in some, 240v in others. Most devices and appliances will happily deal with this variation.
Slight side track here. AC power.
[ I occasionally monitor my power supply by plugging the mutimeter in and observing the voltage feed over a day or two and at different times of day. There can be quite wide fluctuations but that doesn't seem to worry my appliances etc.'] It's power dropouts that are the problem. The resulting surge after a dropout can kill appliances.
One dropout last December killed my Audio mixer, nothing else though. I decided I might get a new mixer as the dead one was about 15 years old. Time for an upgrade. :smokin:]
Ok. V2,V3 and V4 might not respond properly until their under load [ Valves plugged in]. Did you get as far as plugging in the output tubes ?
Maybe try putting in the output tubes then the phase inverter [Valve 4] and then measure V2.[ presuming everything seems alright when you put in the valves ]
I don't know how you got to this but there's no sense in measuring it for AC voltage. It sits between the HT feed and the V1 feed.
Your HT voltage is correct and after passing through the choke, your reading of V1 is 5 volts under the HT. The schematic says it should only be 1 volt difference. At the moment I wouldn't worry about that slight difference. It may change once the other feeds are under load.
Which was ?
Our Power system Down Under [ Aus ] is in the same area as yours . It varies from state to state. 230v in some, 240v in others. Most devices and appliances will happily deal with this variation.
Slight side track here. AC power.
[ I occasionally monitor my power supply by plugging the mutimeter in and observing the voltage feed over a day or two and at different times of day. There can be quite wide fluctuations but that doesn't seem to worry my appliances etc.'] It's power dropouts that are the problem. The resulting surge after a dropout can kill appliances.
One dropout last December killed my Audio mixer, nothing else though. I decided I might get a new mixer as the dead one was about 15 years old. Time for an upgrade. :smokin:]
GoldenVulture
Braindeadologist
Re: Studiomaster Valve Leadmaster violated!!
Here's the voltage feeds at the valves. [ Underlined ]
Here's the voltage feeds at the valves. [ Underlined ]
Re: Studiomaster Valve Leadmaster violated!!
I tried with powertubes now with mixed results.
With the amp in standby all seems normal. The voltages are low, around 170Vdc at the sockets.
When I switch off standby my current limiter lights up real bright.
I've tried with one tube in each of the PT sockets aswell. Same results. Also the fan is barely moving when the power tubes are in.
The preamp sockets seems to be wiring better. I've tried one socket at the time without strange happenings.
If all that tests good go to your power tube sockets.
pin 3 is your plate and is fed by HT via the OT so should be 485v. Pin 4 is fed by V1 via a 470 Ohm resistor [ on each valve ] and should be a little under 484v.
You could also test the other valves sockets for their high tension feed at this point ]
They're all 12AX7's so pins 1 and 6 are the relevant ones. The schematic tells you what each valve should be [ they vary ]
[once you get to the power tubes being in , make sure you have a speaker connected ]
If it's all good , put in the power tubes and connect a speaker and turn it on but don't turn on the standby.[ if you can connect your multimeter to read the HT voltage when you turn it on, do it so you can read if it is firing up properly ] If all is good / no light glow or odd reading on the HT, turn on standby and see if it remains the same.
if all is good Repeat the process by putting in valve4 [ Phase inverter ] then Valve 3 and then valve 2 and then 1.
I tried with powertubes now with mixed results.
With the amp in standby all seems normal. The voltages are low, around 170Vdc at the sockets.
When I switch off standby my current limiter lights up real bright.
I've tried with one tube in each of the PT sockets aswell. Same results. Also the fan is barely moving when the power tubes are in.
The preamp sockets seems to be wiring better. I've tried one socket at the time without strange happenings.
Re: Studiomaster Valve Leadmaster violated!!
Hmm... I'm reading up a bit om current limiters now.
Because regular old style bulbs is so hard to get by these days I had to settle for a 40w bulb. I didn't think about it before, but could'nt the bulb be the problem at the moment? I mean, when the tubes are in, there is a lot more amperage in the amp than when it's in idle. 40w may not be enough for driving the tubes.
Hmm... I'm reading up a bit om current limiters now.
Because regular old style bulbs is so hard to get by these days I had to settle for a 40w bulb. I didn't think about it before, but could'nt the bulb be the problem at the moment? I mean, when the tubes are in, there is a lot more amperage in the amp than when it's in idle. 40w may not be enough for driving the tubes.
GoldenVulture
Braindeadologist
Re: Studiomaster Valve Leadmaster violated!!
[ If you've had it on and then go into standby, all those caps on the HT feeds will be retaining voltage that will slowly dissipate if left in standby ]
Are these the valves that came with it ? If so, chances are they are damaged and need replacing.
I don't use any current limiting when I'm doing such work. Maybe try firing up without your limiting and see how the amp responds.
.
In standby there shouldn't be any HT at any of the valves and the fan is not active. There should only be heater feeds and the Bias being active.
[ If you've had it on and then go into standby, all those caps on the HT feeds will be retaining voltage that will slowly dissipate if left in standby ]
Are these the valves that came with it ? If so, chances are they are damaged and need replacing.
This suggests the tubes are drawing a lot of current and maybe shorting out . Does the Power Transformer start getting warm/hot ? Something in circuit is shorting if it does.
I don't use any current limiting when I'm doing such work. Maybe try firing up without your limiting and see how the amp responds.
.
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