ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

Find of the year...

10/14/1999 2:04 AM
Ken Gilbert	Find of the year... Came across a nugget of treasure today... At work in one of the schools in our district, I noticed that there was a sizeable transformer sitting on a desk in the maintenance office. I left a note on it that said something to the effect of "if this tranny is getting tossed out, let me know." I noticed that there was a HVAC company van outside the school and they were working on the system. Well, wouldn't you know it, they were going to toss it, and one of the maintenance guys told me if I could carry it out I could have it. This was fabulous news, although I still did not know if the windings were good or not. On the old bathroom scale it tips in at 40 pounds. It is of EI type, and on the box that (presumably) the replacement came in, it stated that it was a single phase, 120VAC primary and two 240VAC secondaries, and that it was rated for 1KVA. I got it home, threw it (gently) on the bench and tested for continuity between windings. There was none where there shouldn't be. There was also no continuity between any winding and the core. DC resistances of each winding was under 1 ohm. I applied approximately 40VAC to the primary, current limited by a 150W light bulb. The bulb remained unlit, and I measured 80VAC across both secondaries. I cranked up the variac to the full 120VAC. The bulb turned on dimly and limited the voltage on the primary to about 95VAC, with proportional secondary voltages. I left it that way for about 5 minutes, and the core was still ice cold. There was a small perceptible hum from the core itself. I then cranked the variac back down to 40VAC, flipped off the light bulb current limiter, and slowly brought it back up to 120VAC, without fanfare. I read a solid 240VAC across each of the two secondaries. I would estimate the windings themselves to be of approximately 16 or 18AWG. In a full wave bridge circuit with secondaries wired in series, this tranny would produce about 670VDC at CONSIDERABLE current--at least an amp continuous, with surges 10 times that. The "center tap" formed by the junction of the two windings offers a low impedance tap that could feed the midpoint of two stacked caps, and could feed some signal stages or screens. I could also use each secondary by itself, for 335VDC x 2, great for a stereo situation, or parallel them together for double the current capacity (can you say a fleet of 6AS7's?). In short, I'm pretty excited about this find. I don't know why they were chucking it, but I wasn't afraid to ask on it, and I was rewarded nicely. And though it may not look pretty (no end bells, hack varnish job), it still represents a sizeable chunk of iron that would cost quite a bit of money if purchased. Keep your eyes open for treasures in strange places! KG

10/14/1999 2:04 AM

Ken Gilbert

Find of the year...

Came across a nugget of treasure today...

At work in one of the schools in our district, I noticed that there was a sizeable transformer sitting on a desk in the maintenance office. I left a note on it that said something to the effect of "if this tranny is getting tossed out, let me know." I noticed that there was a HVAC company van outside the school and they were working on the system.

Well, wouldn't you know it, they were going to toss it, and one of the maintenance guys told me if I could carry it out I could have it. This was fabulous news, although I still did not know if the windings were good or not.

On the old bathroom scale it tips in at 40 pounds. It is of EI type, and on the box that (presumably) the replacement came in, it stated that it was a single phase, 120VAC primary and two 240VAC secondaries, and that it was rated for 1KVA.

I got it home, threw it (gently) on the bench and tested for continuity between windings. There was none where there shouldn't be. There was also no continuity between any winding and the core. DC resistances of each winding was under 1 ohm.

I applied approximately 40VAC to the primary, current limited by a 150W light bulb. The bulb remained unlit, and I measured 80VAC across both secondaries.

I cranked up the variac to the full 120VAC. The bulb turned on dimly and limited the voltage on the primary to about 95VAC, with proportional secondary voltages. I left it that way for about 5 minutes, and the core was still ice cold. There was a small perceptible hum from the core itself. I then cranked the variac back down to 40VAC, flipped off the light bulb current limiter, and slowly brought it back up to 120VAC, without fanfare. I read a solid 240VAC across each of the two secondaries.

I would estimate the windings themselves to be of approximately 16 or 18AWG.

In a full wave bridge circuit with secondaries wired in series, this tranny would produce about 670VDC at CONSIDERABLE current--at least an amp continuous, with surges 10 times that. The "center tap" formed by the junction of the two windings offers a low impedance tap that could feed the midpoint of two stacked caps, and could feed some signal stages or screens.

I could also use each secondary by itself, for 335VDC x 2, great for a stereo situation, or parallel them together for double the current capacity (can you say a fleet of 6AS7's?).

In short, I'm pretty excited about this find. I don't know why they were chucking it, but I wasn't afraid to ask on it, and I was rewarded nicely. And though it may not look pretty (no end bells, hack varnish job), it still represents a sizeable chunk of iron that would cost quite a bit of money if purchased.

Keep your eyes open for treasures in strange places!

KG

Replies:

Benjamin Fargen KG, Another case of......... -- 10/14/1999 4:16 AM
anonymous I'd say you are being rewarded for ... -- 10/14/1999 6:38 AM
Mook I'd hate to see the chassis require... -- 10/14/1999 1:33 PM
Don Symes I _know_ Psycho Bass Guy is gonna w... -- 10/14/1999 3:25 PM