Scaling 1/2 Liverpool - oscillations and other bad noises

[El_Martin]

Hi guys!

Finished my first steps in scaling the power of a 15 Watt Liverpool (TeleWreck)

Schematic is like in UR12's (Dana) thread about his liverpool combo.
It's setup like this:
- Bridge rectifier of UF4007s
- first cap (22uF F&T)
- voltage regulator unit w. BUZ 80 A
- 33 uF cap -> to power amplifier
- filter chain

Whole amp is scaled.
First test: good regulation, noise started over 100 V U+

1. I did include the 1N4007 in the schematic, as I wanted to try scaling only the power amp. 470 kOhm from output to ground
Noise stopped, when 1N4007 was bridged w. cable.

2. When testing it today, the noise was present again.
desoldered the 470 kOhm, no effect or maybe worse

Now I'm down to Dana's basic schematic (BUZ 80 A, 6 V Zener, 9,x Ohms series resistor, 100k from gate to 1M pot wiper, no additional resistor to limit lower voltages.

I guess the problem is the regulator sitting between the two caps...
This first cap is very close to the rectifiers to reduce noise (it works, usually)

Any ideas? Increase series resistance?

Ciao
Martin

[UR12]

What are your voltages. Try momentarily shorting accross the 9 ohm resistor and see if the buzz goes away. Do you have any pics?

[El_Martin]

deleted, probs w. i-net connection, duh!

[El_Martin]

Hi Dana!

Voltages at the output side are approx. 325 V when voltage pot is full open. Pretty much the same a without scaling.

What about some small caps across the zener and from input/output to ground?

Its close to the heating wires (thick twisted red/black and the mains (parallel white). The power supply board is rectangular mounted on the right side. Voltage pot is right on top of pic beyond empty turrets.

eyelet board top to bottom (EDIT: pic is upside down, referring to 1st pic)
B+ red wire/bridge (used to be 1N4007)
3 paralle 27 Ohms -> 9 Ohms
100k Ohm
grounded lug screw
6 V Zener

I think I should call it a day, have myself a beer and sleep a bit...


Ciao
Martin

[El_Martin]

Hi!

- inserted UF4007 instead of red wire again
- shorted the 9 Ohm
Dana, you were right ...
No more noise. 0-320 V output.

How about moving that resistor out of the regulation loop? Put it after the zener or simply replace it with a fuse holder?

Transformer is rated 120mA, fast blowing fuses w. 100/125/160/250 mA are right at hand

Whaddyathink?

Ciao
Martin

[UR12]

Hi!

- inserted UF4007 instead of red wire again
- shorted the 9 Ohm
Dana, you were right ...
No more noise. 0-320 V output.

How about moving that resistor out of the regulation loop? Put it after the zener or simply replace it with a fuse holder?

Transformer is rated 120mA, fast blowing fuses w. 100/125/160/250 mA are right at hand

Whaddyathink?


Ciao
Martin

You either need to go lower on your resistance to say a 4-5 ohm resistor or up the voltage on the zener to 7.5 to 10v and that will fix your problem.

[El_Martin]

TNX, Dana!

gonna report the news...

Ciao
Martin

[skyboltone]

I would about triple the size of the first stage filter caps. Ginger had 160uf.
Also, I read somewhere about less than sterling performance from F&T caps..

[UR12]

I would about triple the size of the first stage filter caps. Ginger had 160uf.
Also, I read somewhere about less than sterling performance from F&T caps..

Dan
Where did you see 160uf on Ginger? Ginger has 2 40uf caps in parallel for the first stage filter for a total of 80uf.

[El_Martin]

Hi guys!

Just tested following resistors:
5.1 Ohm up to 200 V no noise, then again noise, maximum voltage 320 V w/o noise
2.5 Ohm up to 200 V no noise, then again noise, maximum voltage 320 Vw/o noise
1.7 Ohm pretty much the same as w 2.5 Ohm

Tomorrow I'll try 1 Ohm (dunno if its too low)
and double first filter cap just for curiosity.

Since the regulator is still between two caps for same (first) node, I'll put the regulator after these two caps.

@skyboltone: since my Liverpool is 2xEl84, there are only 22uF (450 V F&T)+33 uF (500V Illinoise iirc) caps for 1st stage. I prefer lower filtering. Can't complain about the F&Ts. Where did you read negative comments?

How can these 6 tiny lil parts drive me so mad and refuse to work properly

Ciao
Martin
PS: saw a diode backwards across the FET (DS) in another schematic for linear regulators.
PPS: must be the ILL_i_NOISE caps, duh!

[UR12]

I don't know the specs on the BUZZ 80 but if you went down to 1.7 ohms and still got buzz then I would look at replacing the Zener diode with a 10v and keep the 5 ohm resistor. It's like the forward resistance of the Mosfet is too much.

[skyboltone]

I would about triple the size of the first stage filter caps. Ginger had 160uf.
Also, I read somewhere about less than sterling performance from F&T caps..

Dan
Where did you see 160uf on Ginger? Ginger has 2 40uf caps in parallel for the first stage filter for a total of 80uf.

From Alan's post dated OCT 26, 2007 after servicing Ginger:
"Here are some interesting things about her.

She is fitted with a half power swich, basically she uses two cathode resistors/bypass caps, one for each pair. One pair lis lifted from ground for half power.
First stage Resovoir filtering is 160uF, yes 160uF (2x80uF in parallel) !!
The remaining filtering stages use 80/60/60
Filter caps are original and not Mallorys.
Bright switch has one position.
The pots are original and are bog standard CTS (Fender style), not RV4s.
There is a cap/res filter network in parallel with the 100K plate load on the second stage to dump some high end.
Mallory Orange Drop caps were not used at all in this amp. They look like the caps Ampeg were using at the time...LOL
No 9.1K dropping resistors, they were all CC 10K's.
The coupling cap value between stage 2 and 3 is 70nF (a poly and a ceramic in parallel), not 10 or 22 as shown in the schems here.
The coupling cap to the PI entrance is 20nF.
The Presence control is a 5K with 100nF cap.
She has a line out, a pot via a 220K resistor.
The O/T has a 6.6K primary and is the exact same tranny model as an early Express (Nancy) I recently worked on !!!! "

Dan

[skyboltone]

Hi guys!
@skyboltone: since my Liverpool is 2xEl84, there are only 22uF (450 V F&T)+33 uF (500V Illinoise iirc) caps for 1st stage. I prefer lower filtering. Can't complain about the F&Ts. Where did you read negative comments?

I can't be absolutely sure but IIRC it was on the infamouse BBQ site. Maybe I'll just withdraw the comment. If you like 'em fine that's good enuf. eh?

Dan

[UR12]

I would about triple the size of the first stage filter caps. Ginger had 160uf.
Also, I read somewhere about less than sterling performance from F&T caps..

Dan
Where did you see 160uf on Ginger? Ginger has 2 40uf caps in parallel for the first stage filter for a total of 80uf.

From Alan's post dated OCT 26, 2007 after servicing Ginger:
"Here are some interesting things about her.

She is fitted with a half power swich, basically she uses two cathode resistors/bypass caps, one for each pair. One pair lis lifted from ground for half power.
First stage Resovoir filtering is 160uF, yes 160uF (2x80uF in parallel) !!
The remaining filtering stages use 80/60/60
Filter caps are original and not Mallorys.
Bright switch has one position.
The pots are original and are bog standard CTS (Fender style), not RV4s.
There is a cap/res filter network in parallel with the 100K plate load on the second stage to dump some high end.
Mallory Orange Drop caps were not used at all in this amp. They look like the caps Ampeg were using at the time...LOL
No 9.1K dropping resistors, they were all CC 10K's.
The coupling cap value between stage 2 and 3 is 70nF (a poly and a ceramic in parallel), not 10 or 22 as shown in the schems here.
The coupling cap to the PI entrance is 20nF.
The Presence control is a 5K with 100nF cap.
She has a line out, a pot via a 220K resistor.
The O/T has a 6.6K primary and is the exact same tranny model as an early Express (Nancy) I recently worked on !!!! "

Dan

Dan

I guess that could be true as there is a note on Mark Abbott's Liverpool schematic regarding different cap values and he did mention a 160 uf. I have'nt had the luxary of looking at the real Ginger but it seems very odd to me that the pics I have seen show some grey caps. There are 5 in the stack and one on the power supply board. The Grey ones on the bottom of the stack are all the same size and if I take the Fuzzy Ginger pics and measure the number of hole next to the length of the bottom cap I ger 10 holes long. That is 2.65 inches. I would think a 80uf 450v cap back in 1981 would have been longer that that or bigger in diameter. I would be more inclined to believe that there were two 80uf 350v (physically smaller) caps in series which would give you a total of 40uf at 700v. Maybe Allan took some better pics that he could post to prove what he thinks he saw.

[Richie]

looks like a 22uf 450 rubycon on the PS board from the pics .