Junkbox VD - 9 in 9 out issue

[stonerbox]

Hi!

Edit: turns out top leg of C7 had a bad connection.

Zero increase in voltage is today's problem, actually goes down from 9.98 V in to 9.45 V out. I subbed the BC557 with a 2n3906 but use BC547C for the rest.
I swapped all transistors once just to be sure but and have also checked all connections (continuity), all cuts and the pinout of 2n3906, no problem there. I'm sure it just some very simple mistake on my part. Any ideas?

Q1
C 9.94
B 0.56
E 0.003

Q2
E 0.003
B 0.056
C 0.003

Q3
C 0.056
B 0.702
E 0.003


Q4
C 0.052
Q 0.703
E 0.003




https://www.diystompboxes.com/smfforum/index.php?topic=97141.0

[stonerbox]

Guess I was not done after all. When I measure the output it reads 16.2 volts, no problem there, but when I hook up the output to four opamps (buffers and filters) the volt goes down to 7 volts and Q1 gets very hot. I tried swapping Q1 but with the same results.

Q1
C 9.0
B 4.2
E 4.1

Q2
E 4.1
B 4.2
C 0.0

Q3
C 4.2
B 0.69
E 0.0


Q4
C 0.05
Q 0.70
E 0.0


When hooked up to OP-amps

Q1 Gets very very hot (have swapped same result)
C 8.99
B 2.5
E 2.4

Q2
E 7.5
B 4.1
C 0.0

Q3
C 0.052
B 0.69
E 0.0


Q4
C 0.05
Q 0.70
E 0.0

[iainpunk]

what opamps did you use?
this design can deliver only very little current, so driving more than a low current transistor circuit will suck the voltage down to 9v or even lower.
shouldn't expect much form something called ''junkbox''

cheers

[stonerbox]

what opamps did you use?
this design can deliver only very little current, so driving more than a low current transistor circuit will suck the voltage down to 9v or even lower.
shouldn't expect much form something called ''junkbox''

cheers

I had my suspicions that was the case.. well I use five OPA2134. Are there any better alternatives (voltage pumps) out there?

[iainpunk]

LOTS of options out there, just look at the Centaur circuit, it uses a dedicated chip, and google might help as well, look for ''charge pump'' circuits/chips.

cheers

[stonerbox]

What about something like this? I got some CD4049s lying around and I am pressed for time and do not want to wait for an order of NE555s to arrive. Or would this one not produce enough current?
'

https://circuits-diy.com/12v-to-24v-voltage-doubler-circuit-using-cd4049-ic/

[iainpunk]

rule of thumb for most CMOS is an output current of less than 2mA per output, putting 4 parallel like this should give about 8mA, again, fun if you have a low current transistor circuit, but not useful for driving opamps.

for comparison, that OPA2134 can output 35mA.
not to say you should use that opamp for the charge pump, but to give you an idea of scale.
another comparison for schale, the NE555 can deliver 200mA of current, which is quite capable of driving a charge pump.

cheers