New to the Forums. With Questions of course.

[morbe]

Hey everyone Im new to the forums and this site in general Its great, Im glad I found it. I've been jamming for a few years now and I've pounded out some simple Pedal mods and built low voltage opamp circuits Im certainly no amp tech but I know my way around electronics and circuits I just dont really like to mess with high voltage stuff for obvious reason though I have repaired simple things on high voltage items its not my area of expertise. But I do have some questions about a PA that my band recently uses that is starting to die.
The only thing that I know it its a "Tosh" and its over 25 years old. and has been repaired twice. Its was being used only for Vocals but last time we used it we started to smell burning electronics that came from the PA. The PA still Works It still Amplifies well, I sing and play guitar and was still able to do so with out electrical shock but when we pinpointed the smell from the amp for safety reasons we powered the PA down. again it amplified well it just started to give off a smell that eventually passed and started to give off an osculating white noise like it had a built in phaser. We are getting a new PA but I know that the guy who owns it will just give it to me, but What can I do with it? Throw it out?

[nickb]

H it just started to give off a smell that eventually passed and started to give off an osculating white noise like it had a built in phaser. We are getting a new PA but I know that the guy who owns it will just give it to me, but What can I do with it? Throw it out?

Welcome to the forum.

If ever you smell burning, it's time to switch off and get a repair. Not doing so always makes this more difficult, expensive and could be dangerous.

You can ask for help with fixing this amp but you will help everyone if you can provide the model number andpost in the Maintenance, Troubleshooting & Repair forum, attach the schematic so we all know what you are looking at.

Nick

[morbe]

Thanks I will post this where it needs to be posted.

[ElHefeNeuroso]

Hi everyone,

I`m Ivo from Split, Croatia.
Could anyone give me some advice regarding these two parts for my Peavey Tour 700 bass amp... It looks like it`s impossible to find these in my country so any advice would be most usefull...Thank you

Peavey Tour 700 schematics.pdf

BILL OF MATERIAL REPORT - TOUR 700 POWER AMP
Qty. Part # Description Reference Designators
2 30320574 5600UF 125V 20% EL SNPH3 C30 C31

[ElHefeNeuroso]

Her`s a photo...

[Steve Conner]

5600uF, 125V is a non-standard rating. I suggest you get a 4700uF or 6800uF, 160V.

What makes you think the caps need replacing anyway? Have you tested them? How?

[ElHefeNeuroso]

5600uF, 125V is a non-standard rating. I suggest you get a 4700uF or 6800uF, 160V.

What makes you think the caps need replacing anyway? Have you tested them? How?

Thank you for your reply.

Unfortunately I don`t know much about electronics .The guy doing the repair said the caps are causing the problem so I kind of took his opinion on the matter for granted. I really don`t have a clue how he does the testing. What would you advise for replacement caps? These 4700uF or 6800uF and how could the difference in voltage and capacity affect the overall performance of my amp?

Thank you once more....

[J M Fahey]

One of them *looks* like it has a cracked leg.
1) what is the actual power rail voltage in that amplifier?
I bet it's around 70/80V, no more; in that case you can use 100V electrolytics which are far more common.
I fear a 160V one, same capacity, will not fit in available space.
2) Peavey sell you any original parts you wish, for a reasonable price, and will probably airmail them direct to you, if you get an International Credit Card, valid in the USA.
3) maybe you can buy them through the local Peavey representative, but it will take a lot and perhaps price will double or triple.
4) If 5600x100 will do:
electrolytic capacitor Aluminum Electrolytic Capacitors | Mouser
5) if you jump to 5600x150V , they become *EXPENSIVE* and *HUGE*, so I'd recheck rail voltage first.
electrolytic Aluminum Electrolytic Capacitors - Screw Terminal | Mouser

[ElHefeNeuroso]

One of them *looks* like it has a cracked leg.
1) what is the actual power rail voltage in that amplifier?
I bet it's around 70/80V, no more; in that case you can use 100V electrolytics which are far more common.
I fear a 160V one, same capacity, will not fit in available space.
2) Peavey sell you any original parts you wish, for a reasonable price, and will probably airmail them direct to you, if you get an International Credit Card, valid in the USA.
3) maybe you can buy them through the local Peavey representative, but it will take a lot and perhaps price will double or triple.
4) If 5600x100 will do:
electrolytic capacitor Aluminum Electrolytic Capacitors | Mouser
5) if you jump to 5600x150V , they become *EXPENSIVE* and *HUGE*, so I'd recheck rail voltage first.
electrolytic Aluminum Electrolytic Capacitors - Screw Terminal | Mouser

Wow! Thanx a lot for all the info!!! I actually got in contact with a Peavey dealer in Croatia and it turns out they are able to place an order for the exact component...I just have to wait for 2 months!!!
I have some options for a replacement amp in the meantime but if that fails i`ll most certainly try out those links you provided!
Thank you so much!

BTW. I have an option to buy Ampeg SVT 3 Pro..Does anyone have experience with those?How reliable are they compared to this Peavey for example?

[ElHefeNeuroso]

Wow! Thanx a lot for all the info!!!The leg is not cracked..it`s just a crappy photo. I actually got in contact with a Peavey dealer in Croatia and it turns out they are able to place an order for the exact component...I just have to wait for 2 months!!!
I have some options for a replacement amp in the meantime but if that fails i`ll most certainly try out those links you provided!
Thank you so much!

BTW. I have an option to buy Ampeg SVT 3 Pro..Does anyone have experience with those?How reliable are they compared to this Peavey for example?

[J M Fahey]

If the legs are not cracked, what is the actual problem with those caps ???????????????
What was the original problem with your Peavey ??
PS: since you seem to have it, can you please post the *full* Tour 700 schematic or Service manual?
It may help others.

[ElHefeNeuroso]

I really don`t know what is the problem with the caps since electronics are not my area so I `m just going along with what i was told by the guy that is fixing the amp.
The amp would work fine for a while and than the Clip/protection would light up and the amp would produce loud humming noise.
This happened once before and i took the amp to this guy. He said its these electrolytes but that he was able to "save" them and after that the amp worked fine for a month...and than the same thing occurred!

here`s the schematics for Peavey Tour 700...I actually think I might have downloaded it from this forum :-)

tour700.pdf

[J M Fahey]

OK, thanks.
What a *weird* amplifier.
*Sort* of a Class H (or some close letter) Low/High +/-V rail voltage ... but the switching element is not a transistor or a Fet , plus some high current and voltage, ultra-fast diode .... it's a *relay* , which to boot switches transformer secondaries.
"Clunky" is the understatement of the year.
Literally, it will go "clunk ... clunk ..." as you play.
I once experimented something similar, basically as a joke, to make an amp which had incredible "bench" specs ... when tested with an oscillator, that is.
A continuous tone was long enough (obviously) for the relay to switch and raise the transformer voltage, lost in part because of high current consumption .
In fact I switched primary taps, similar to what a voltage stabilizer does, but the basic principle is exactly the same.
But on *musical* signals ... forget it.
Even worse, just imagine the poor relay trying to catch up with a slapping tapping bass player.

PD: I *hope* elhefeneuroso's problem is not just this relay starting to fail.
I would check this circuit and scope +/-V rails under load, with varying program input, just in case.
With the circuit working properly, I'd expect to see jumping voltages, big way and in this case it would not indicate a fault.

[ElHefeNeuroso]

It`s obvious that you know your electronics! :-D

Would you be so kind to explain to me those amp "classes"
?!

[oc disorder]

Hi ElHefeNeuroso - here's some light ? reading that may be illuminating

Amplifier classes

Class A - Exposed and Explained by Randall Smith

This is directed at RF (radio frequency) amplifiers but same principle
Classes of Amplifier Operation

Amplifier Classes : Class A, B, AB, C, D, E/F