A friend asked me to help him with his Peavey amp that wasn't working and he went to a few shops over the years and he didn't have any luck. When you tried to play sound through it the B+ dropped way down and drew excessive current. I found the output transformer was shorting under a load. I hooked up a Jolida transformer from an old amp I had laying around and everything worked as it should. But it's only a 50 watt transformer and this amp is 100 watts. He ordered this Hammond 1650t and I hooked it up for 8 ohms. You tie the green wire with the green/yellow and the black with the black/yellow take the positive off the yellow and hooked speaker ground to the black and it has low sound coming out. I did hook the Jolida up a second time to make sure I'm not crazy and it works great with plenty of volume.
This transformer is a bit different than the ones I've used in the past as the extra winding is added to allow it to be used with more power I believe? Am I missing something and just not hooking this thing up properly? I'm inputting a 1 khz test, I even tried just hooking it up as a 4 ohm and taking the positive off the green/yellow and it seems only slightly more sound. Thanks for any help or guidance you can provide. I did check the preamp section and the signal passes through clean and all the voltages and bias are good and stable.
This transformer is a bit different than the ones I've used in the past as the extra winding is added to allow it to be used with more power I believe? Am I missing something and just not hooking this thing up properly? I'm inputting a 1 khz test, I even tried just hooking it up as a 4 ohm and taking the positive off the green/yellow and it seems only slightly more sound. Thanks for any help or guidance you can provide. I did check the preamp section and the signal passes through clean and all the voltages and bias are good and stable.
I took a picture of the transformer layout so someone wouldn't have to download the pdf. I haven't seen an output with the extra winding before but I tried to hook it up like it shows for 8 ohms and 4 ohms but the volume is very low. It seems like they may have switched the colors of the wires or I'm just not looking at this correctly. As I mentioned hooking up the Jolida transformer works fine.
Try connecting to only blk/yel and yel, leaving the other half floating. Then try grn and blk only. See of both give sound. Then try connecting in series for 16 ohm. if that gives low sound, but does NOT result in excess current the transformer is actually ok. Just reversed phase on the green-black winding. If the 16 ohm connection gives low sound but also high current then the transformer does indeed have a short in it.
The current may be a little high when strapped for 16 ohm with an 8 ohm speaker, but nowhere near as high as with a short or pair of out of phase windings paralleled. Short term impedance mismatch won’t hurt anything.
The current may be a little high when strapped for 16 ohm with an 8 ohm speaker, but nowhere near as high as with a short or pair of out of phase windings paralleled. Short term impedance mismatch won’t hurt anything.
It is wired up wrong. Disconnect what you have done and do this:
Connect the Green to the Black and yellow.
Black is common, Grn&Blk/Yel is 4 Ohms, Grn/Yel 8 Ohms and Yel is 16 Ohms.
Connect the Green to the Black and yellow.
Black is common, Grn&Blk/Yel is 4 Ohms, Grn/Yel 8 Ohms and Yel is 16 Ohms.
Thank you Jon and Ski for your replies but I tried the ways to hook it up that you both suggested and I just get a low tone which I believe is just residual audio bleeding over and it's not driving the transformer to turn on. The UL taps are not used from this transformer for this design because it uses a dropping resistor to provide voltage for the grids, the original transformer didn't have ul taps and I didn't use them on the Jolida and it works fine. Even using the blk and grn taps only it's the same thing. It makes me think they have wired this thing incorrectly or used the wrong wires. It is a brand new transformer from digikey.
I just did some resistance checks and I didn't see anything abnormal at least not as far as I was concerned.
blue to red 24 ohm
red to brn 22 ohm
Blue to brn 46 ohm
yel to green/ye l .1 ohm
grn/yel to blk/yel .1 ohm
Yel to blk/yel .3 ohm
blk/yel to grn open
grn to blk .2 ohm
blue to red 24 ohm
red to brn 22 ohm
Blue to brn 46 ohm
yel to green/ye l .1 ohm
grn/yel to blk/yel .1 ohm
Yel to blk/yel .3 ohm
blk/yel to grn open
grn to blk .2 ohm