Ampeg PB250 Schematic

Moreheadroom · #1 07-04-2010, 12:02 AM

Hello all, With hat in hand I have joined your great community to ask for assistance. I have been searching for a schem for an Ampeg PB250 Portabass head for more hours now than I dare to admit! I think I may have found one for nearly every other ampeg ever made. Starting to think - either these things don't break, or they don't get fixed, or someone at ampeg ate the original schematics when production finished!!.....seriously though, this is clearly the go to info world of bass and would really appreciate any help. Just brand new here and hope I have the right forum and asked nicely??? Thanks MH

Jerrold Tiers · #2 07-04-2010, 08:42 AM

I have them (of course!).

You just collecting, or you have a problem that needs to be fixed?

Moreheadroom · #3 07-04-2010, 03:09 PM

Wish I was a collector. Amp is very much alive and well. Just want to get from 120 to 240v and do away with the transformer I've been lugging around. I'm sure I read somewhere last year on TB these were a multitap transformer? But without the schem anyone is just looking for trouble moving leads inside this little box. If it can't be done - it's not the end of the world I guess. Would really love any help you can offer Thanks

BassmanPaul · #4 07-04-2010, 05:22 PM

Any decent tech will be able to tell you if the amp has a switchable primary. There is only a couple of ways to do it.

Paul

Moreheadroom · #5 07-06-2010, 01:49 AM

I would have thought so too. I took it to a tech that was pretty well spoken of by some fairly fussy people I know, but he wasn't that keen without a drawing. Can't blame him I guess. I'd rather someone leave it alone than cook it. Be cool to even just have the primary section to walk into the tech with. Don't really feel like spending more money for another zero result. Mick

Jerrold Tiers · #6 07-06-2010, 06:48 AM

I am pretty sure the PB250 and PB800 had dual primary transformers.

it is EXTREMELY SIMPLE to see if that is so, and if your tech can't decide what it is, then NEVER GO BACK TO THAT TECH.

You only need to look at the mains connection......and count . if the transformer has two mains wires, it is one voltage only. If it has more, then it is at least 115/230 and can be converted.

I will check, just to be sure that I can say with certainty.

Moreheadroom · #7 07-06-2010, 02:43 PM

Thanks mate,
That would be awesome, and yeah if it is that simple - I won't be going back. Mick

Jerrold Tiers · #8 07-06-2010, 08:53 PM

OK, I checked.....

I couldn't recall if there might or might not have been a 120V version, but we NEVER HAD A PART NUMBER FOR THAT.

All we had was a universal type, 94-012-40. The "94" is for a transformer or coil, and the "-40" in the part number means it is a "universal export" type.

So ALL PB250 units are capable of all using all the common export voltages including 230/240.

I guess maybe I was a LITTLE harsh...... but the presence of a bunch of mains wires means he should have been able to KNOW it was re-connectable, even if he wasn't sure HOW to do it. And looking a little farther would tell him that.

In fact, with stuff he should already have, he ought to have been able to figure out the complete correct connections for any voltage...... even with NO extra information.

I can forgive him for wanting to see some form of diagram etc, but a good tech is one who can go beyond the "ugh... part black and burned, must replace part" level, and ought to know at least how to deal with series windings and parallel windings. it's pretty much like speakers in parallel and series, actually.

Dunno, maybe I expect too much....... I worked as a tech while in school, and made good money fixing stuff the boss couldn't.

rbonner · #9 07-06-2010, 10:13 PM

Fear, have to get past the fear.

BOB

danomite64 · #10 07-07-2010, 06:38 AM

Jerrold, I'd like a copy of that schematic myself, just in case my PB250 gets sick. I've been using the hell out of it for five years now, and wouldn't want to be without it.

BassmanPaul · #11 07-07-2010, 09:45 AM

Quote:

Originally Posted by Jerrold Tiers

I guess maybe I was a LITTLE harsh...... but the presence of a bunch of mains wires means he should have been able to KNOW it was re-connectable, even if he wasn't sure HOW to do it. And looking a little farther would tell him that.

In fact, with stuff he should already have, he ought to have been able to figure out the complete correct connections for any voltage...... even with NO extra information.

I can forgive him for wanting to see some form of diagram etc, but a good tech is one who can go beyond the "ugh... part black and burned, must replace part" level, and ought to know at least how to deal with series windings and parallel windings. it's pretty much like speakers in parallel and series, actually.

Dunno, maybe I expect too much....... I worked as a tech while in school, and made good money fixing stuff the boss couldn't.

No you were NOT too harsh. If this guy is taking money from people he should be competent and professional.

You either have two 120V primaries, sometimes with a tap at around 110V, A tapped primary: 0 100, 120, 230, 240 etc or you have a single primary. Sorting out which you have is tech 101 stuff. He should know this like the back of his hand!!

Paul

Jerrold Tiers · #12 07-07-2010, 09:03 PM

Them as wants schematics should PM me an email.

The schematics don't include the transformer, I'm looking around for the transformer spec to see if it has 6 or 7 wires.

Moreheadroom · #13 07-09-2010, 05:27 AM

Thanks fellas - for all your good oil. Yeah, it was the 250 thank you Mr.Tiers....You are a gentleman. Yoda to all things Ampeg - seem it would!!
Mick

danomite64 · #14 07-09-2010, 10:23 PM

Thanks, Jerrold!