(another) problem with the PT-80

[Pierre]

Hi !!!!
i did not wanted to "invade" another topic with this one...
I have the PT-80 done, and i have this strange (to me) problem...
I'm powering with a charge pump (GGG's loyaut), and when i conect it to my Ultra Clean PS it literally sucks half of the power...i mean, without the effect plugged in, it messures (the PS) 9.5V, the carge pump gives me 18V...The transformer in the Ultra Clean is a 425mA, so, i dont think it is an amperage issue...But when i plug the PT-80 in ,after 10 seconds  power starts  droping to 4.5 V...and i can only hear dry signal without any effect...
I tried with 2 batteries and power and nothing...
I tripple checked all the circuit looking for a short circuit, and nothing, it's all clean. I change all 4 electrolitics caps and nothing...Changed voltage regulators, and nothing...
The only way i could have the echo effect was with a cheap 16V...but after working for a short time, echo effect just fade away, having now only dry signal with the effect on...I tried the PT 2399 chip in a Rebote Delay and it's working good, the same with the TL 072...Can it be the SA 571 the source of the problem?
I repeat, all solders are clean and  there's no bridges in the traces...
I used GGG's loyaut for 3pdt switch without any mod...

If i cant debug this one, im plannig to build another one (i allready have a second pcb)...in that case, can i use tantalum caps for the 1µF?
and ceramics for all the others?
Thanks for your patience (with my limited english vocabulary ) and for your help !!!

[RDV]

When you use the cheap 16v, are you hooking it up past the charge pump, or in front of it? If you can bypass the charge pump and use the 16v transformer and it works, then it's the charge pump that is the problem.

HTH

RDV

[RDV]

...also, what is the voltage rating of the cap used in your charge pump? 10volts would be bad, 16volts maybe bad, 25volts of higher would be  good.

[Pierre]

thanks for answering !!!
Caps in the charge pump are 63V rating ,so, no proplem there...
When i used the 16V PS, i did not use the charge pump...i though that the problem was in fact in the charge pump untill the effect just stop working  with the 16V PS...When i tried with too batteries hoocked toghether, they just died in a few minutes and so the batterie in my multimeter...
Annyway, i liked this one very much (the time it worked) and i'm going to buil a new one. The thing is, i allready have 1µf tantalum caps and  a bunch of ceramic caps...i was wondering if this caps will have anny negative effect in the tone...

[RDV]

I think you should debug this one 1st. You've got a short to ground somewhere. Find a magnifying glass and have a good look at your PCB again. You'll find it. Patience is your friend. I'd suggest checking from the 5volt regulator onward first since you still have the straight sound when the echo dies out.

RDV

[Pierre]

thanks again !
i swear i checked with a magnifying glass a hundred times and i really cant find annything wrong...

[RDV]

Time for another of my stories. 

When i built mine, it didn't work at all. I did everything that I've advised you to do and just couldn't find the problem. I thought it was my old Ibanez 18volt adapter that came with my CS-505 not having enough current, so I ordered a brand new Dunlop ECB-04 which is the perfect adapter for it, but alas, still no delay. Just dry signal. I then had to have that 101st look, and decided to do a component value check, which led to my discovery of about 3 film caps that had one too many(or too few) zeros in the values. Well, needless to say, it worked perfectly after replacing them.

The End

It's there somewhere, it's a proven circuit.

RDV

[cmat]

HAH!  I just finished a Ross I had laying to the side that I had looked at 100 times and on the 101st I found one resistor that was the wrong value.  I changed that 1 resistor and BOOM compression.

[Paul Perry (Frostwave)]

maybe it is time to start poking the various components lightly with a damp finger and listening for the sizzle, because the only way the supply can drop (on batteries) is via a component overheating, or a short circuit somewhere.
Or maybe there is a bias mistake, (like a voltage splitting resistor pair with bad values) resulting in a bias voltage gradually going out of whack. But that shouldn't cause the supply to come down, even so.

[guitar_199]

I haven't looked at the circuit......but perhaps a reversed electrolytic cap?  Or some other polarity sensitive part?

[Pierre]

no. AGH !!
i have checked all components, resistors values, cap values and polarity, and nothing is wrong...
The charge pumps still working good, the Ultra Clean too...but once i plug the PT-80, the same problem...  i still having straight signal with the 16V wall mart but no echo...voltage regulators are doing their job ( i have noticed that the 5V regulator is getting a little hot)...so, i going to put toghether the components for a new one...(this one is going to be hide and forgeted )...I ordering a new SA571 or maybe im going to try with a NE 570...im just wondering if putting tantalum caps instead the NP 1µF caps will have a bad effect in the tone quality...

[RDV]

...im just wondering if putting tantalum caps instead the NP 1µF caps will have a bad effect in the tone quality...

Just get that polarity right.

RDV

[RDV]

I have noticed that the 5V regulator is getting a little hot.

Something is shorted in line with that.
Have you tried another compander?

RDV

[RDV]

Your problem is definitely around the delay chip if the 5v reg is getting hot.

RDV

[Pierre]

...no, im ordering a new compander right now...I now for shure that the PT 2399 is working good since i have tried it in a Rebote delay...

[oli]

Hi,

it is quite normla, that the voltage regulator is getting a little hot - btw waht is "a little" hot?
One hint: this PT-80 also works with 9V supply voltage (mine does) - no need for a charge pump. Try to bridge the charge pump circuit.
Regards,
Oliver

[Pierre]

Hi !, its me again

well, i decided to build another PT-80, i could not find the problem in the firts one, so, i put all new parts toghether in a new pcb...this time i decided to try the DPDT switch instead of the loyaut for the 3PDT...Well, after one or two minutes, it just stop doing the echo, only dry signal, voltage from the PS droped to 4.5V...
...so, it was not the PT-80  ...
The PS is the Ultra Clean, wich works fine, giving 9.5V to 4 or 5 pedals (i use a 400mA transformer)...
Charge Pump gives me 18V, regardless if the PS is powering other effects...but few instants after pluggin the PT80 (without powering any other effect ) problem appears...
Electrolityc caps in the Charge Pump are 63V,and since i have 18V in the output, i guess diodes are( 4002's) are correctly oriented...
Im shure that the problem is in the pump, but i cant find anything wrong...
Now i have 2 PT-80, working just fine powered with a cheap, unregulated 12V (16V in the real life) PS...
Im planning build a 18V PS, but i wish i could find the problem...

[RDV]

At least now you've got 2 PT-80s.

Mr. Brightside

[Pierre]

yeah !
i'm thinking the same  ...i wonder what can i do with two PT-80

[Paul Marossy]

I just finished a Ross I had laying to the side that I had looked at 100 times and on the 101st I found one resistor that was the wrong value.  I changed that 1 resistor and BOOM compression.

Been there, done that. That's why I like to put things like that aside for a while. Most of the time, when I come back to it, my mistake slaps me in the face and then I slap my forehead! 

I've been thinking about trying the PT-80 or Rebote Delay sometime. I guess that'll be one goal for 2006.