new build 36lite with vvr

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Re: new build 36lite with vvr

Post by Bieworm »

chaliapin wrote:
Sat 01/14/23 5:10 am
It was a bad thing...

Where does the voltage at the cathode pin come from? There wouldn't be anything there with no tube in the socket right? I seem to have am intermittent short/ problem in the power section, back to the bulb limiter, with a power tube in place the light dims after the standby is switched on but then slowly brightens again...
You did connect your OT red wire to node A on the HT I hope?

Also… the primary connections from wall power to PT is very confusing. Triple check if that’s ok.
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Re: new build 36lite with vvr

Post by chaliapin »

Thanks bieworm yes, red wire in the correct position. The first diagram you've drawn is the correct 240v hookup for the PT, but what's the second?
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Re: new build 36lite with vvr

Post by Bieworm »

Both for PT’s. One for a 0-240V prim and one for a 0-120 / 0-120 universal US/EU hammond
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Re: new build 36lite with vvr

Post by chaliapin »

So blue live, white neutral, the other way round from the handwriting on the Danbury sheet I posted a few posts back. Assuming you're right then I connected it back to front, I'll take a look at it tomorrow. Thankyou do much ,
Mike
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Re: new build 36lite with vvr

Post by chaliapin »

It doesn't seem to matter the polarity of the pt mains connections which is maybe why I have contradictory information. Either way it's giving 290 at the rectifier, 4.5 rectifier heater and 6 at the heater circuit. All following voltages are WITHOUT light bulb limiter, pre amp tubes installed, rectifier installed, NO power tubes installed, power and standby ON. No speaker connected.

V1
P1 166v
P3 1.3v
P6 166v
P8 1.3v

V2
P1 240v
P2 40v
P3 85v
P6 247v
P7 42v
P8 85v

V3-6 no valves installed

P3 0v
P7 400v
P9 390v

Voltage at points
A 398
B 388
C 330

To my uninformed way of thinking nothing seems way off here. But bad things happen when I install 2 power tubes and flick the standby. Gradually increasing hum (volume on zero) power tubes getting bright and hot after a few seconds, then I turn the standby off again before something goes bang...
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Re: new build 36lite with vvr

Post by JMPGuitars »

chaliapin wrote:
Sun 01/15/23 6:44 am
To my uninformed way of thinking nothing seems way off here. But bad things happen when I install 2 power tubes and flick the standby. Gradually increasing hum (volume on zero) power tubes getting bright and hot after a few seconds, then I turn the standby off again before something goes bang...
Voltages can't be correct without all tubes in, so you're not getting the full story. Anyway, from your description, it sounds like you need to do another CAREFUL / PATIENT highlighter test.

You should test your voltages with all tubes in after doing your highlighter test again. Then you can see what your tube dissipation is.
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Re: new build 36lite with vvr

Post by chaliapin »

Yup. Careful and patient. Did all the resistors and caps earlier will print another schematic and highlight again. Are my yellow vishay caps the right way round? Band towards negative?
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Re: new build 36lite with vvr

Post by JMPGuitars »

chaliapin wrote:
Sun 01/15/23 11:37 am
Yup. Careful and patient. Did all the resistors and caps earlier will print another schematic and highlight again. Are my yellow vishay caps the right way round? Band towards negative?
Those lines are meaningless. The only current company that I'm aware of that marks the outer foils is SoZo.

If you want to orient the foils correctly, you need to determine which side is the outer foil with an oscilloscope. Then you point the foil to 1 of 3 things: ground; the previous stage's anode; or B+. Which one of those 3 things you point to is dependent on which is the path of lowest impedance.

In any case, that will help reduce noise, but won't solve any actual circuit problems.
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Re: new build 36lite with vvr

Post by Bieworm »

chaliapin wrote:
Sat 01/14/23 4:35 pm
So blue live, white neutral, the other way round from the handwriting on the Danbury sheet I posted a few posts back. Assuming you're right then I connected it back to front, I'll take a look at it tomorrow. Thankyou do much ,
Mike
Yes, but did you follow the wires from the mains power correctly?
Live to fuse, fuse to on/off switch, switch to white on PT, bue from PT to neutral on wall power.
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Re: new build 36lite with vvr

Post by chaliapin »

Pretty sure yes.
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Re: new build 36lite with vvr

Post by chaliapin »

Did another highlighter test, every resistor read or tested, all caps bar two little ones on the board and the two across the pots read or tested, all connections and wiring checked.

Only differences from 36w lite schematic are

No ground on OT
1k5 resistor between A and B
Drain resistor 100k
V3 and v6 p3 tied
V4 and v5 pin 3 tied.

It's not just because I have only one valve of each power tube pair in is it? I have an 8 ohm speaker in the 8 ohm output socket.
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Re: new build 36lite with vvr

Post by JMPGuitars »

chaliapin wrote:
Sun 01/15/23 2:10 pm
Did another highlighter test, every resistor read or tested, all caps bar two little ones on the board and the two across the pots read or tested, all connections and wiring checked.

Only differences from 36w lite schematic are

No ground on OT
1k5 resistor between A and B
Drain resistor 100k
V3 and v6 p3 tied
V4 and v5 pin 3 tied.

It's not just because I have only one valve of each power tube pair in is it? I have an 8 ohm speaker in the 8 ohm output socket.
You should ground the OT. This should done by running the OT negative to the output jack ground lug, and run a ground wire from the output jack ground lug to the power amp star ground.

Drain resistor should be 220k. 100k is too low.
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Re: new build 36lite with vvr

Post by chaliapin »

I had the 16 ohm and the ground the wrong way round on the bloody output jacks!

Probably didn't do my OT any good...


Id misslabeled the colours on my schematic and layout. Eugh.

Anyway, with two power tubes in the bulb isn't dimming much now after switching the standby on so something still up I think. Tried without limiter again whole thing got pretty warm pretty fast...
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Re: new build 36lite with vvr

Post by chaliapin »

Im so close! Amp is working fine with the limiter, b+ around 160v so sounding flat and clean with guitar but doesn't sound like anything is wrong. Without limiter all seems fine for a few seconds after standby switched then loud hum getting progressively louder and tubes rapidly getting pretty warm...Took a few quick readings before switching off, b+ good, cathode voltage slowly went up and I switched off around 13 or 14v, not sure what's up now, maybe it's all fine and I need to find the source of the hum?
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Re: new build 36lite with vvr

Post by JMPGuitars »

chaliapin wrote:
Sun 01/15/23 6:19 pm
Im so close! Amp is working fine with the limiter, b+ around 160v so sounding flat and clean with guitar but doesn't sound like anything is wrong. Without limiter all seems fine for a few seconds after standby switched then loud hum getting progressively louder and tubes rapidly getting pretty warm...Took a few quick readings before switching off, b+ good, cathode voltage slowly went up and I switched off around 13 or 14v, not sure what's up now, maybe it's all fine and I need to find the source of the hum?
You need to read stable voltages. Use one of the voltage charts from the downloads section, and post the results here. I can't comment on voltages without seeing them. Your cathode voltage needs to be a stable reading (with no guitar / signal input). That means let the amp warm up for 1 minute, turn standby off (B+ active), and test your voltages.

All knobs she be turned down to zero.

You might want to do another highlighter test, and check the solder connections along the way.
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