CIHFA1 amp replace output transformer

[prime]

Hi guys i have a faulty output transformer on my amp, i got a replacement from Mouser, I am in the process of swapping it out but have a wire that im not sure of. On the original output on the secondary side there are three wires for the 70vlt tap, i dont need them so no problem, my issue is i see there is also an orange wire that goes to c129 and r152. Is this wire also for the 70vlt tap?  on my new output on secondary side i have a white for 16ohm, a yellow for 8ohm, a grn for 4 ohm and a black, im sure the black is for ground, no other wires.   thanks pete

[jukeboxmarty]

The orange wire is for 'inverse feedback' and according to Seeburg is necessary to "ensure a minimum of distortion and hum". It feeds into the cathode of V104 the 12AX7 Amp/Phase Splitter. It usually is attached to the secondary at the highest wattage tap. I've never replaced a Seeburg output transformer with a contemporary replacement, but I would try attaching this to the 16 ohm tap. The amp will run without the orange wire attached, but the result will probably be over-driven and distorted.

[prime]

So glad i asked, i will connect it to the 16 ohm wire, thanks pete

[prime]

Aug 25, 2022 22:26:23 GMT jukeboxmarty said:

The orange wire is for 'inverse feedback' and according to Seeburg is necessary to "ensure a minimum of distortion and hum". It feeds into the cathode of V104 the 12AX7 Amp/Phase Splitter. It usually is attached to the secondary at the highest wattage tap. I've never replaced a Seeburg output transformer with a contemporary replacement, but I would try attaching this to the 16 ohm tap. The amp will run without the orange wire attached, but the result will probably be over-driven and distorted.

Hi Marty, i connected the transformer and have an issue,    on my new transformer i have a blue, blu/yel, Red, brn/yel, brn on the primary side on secondary i have wht, yel, grn, blk.  As per schematic for transformer blue goes to plate, blu/yel goes to screen, red to B+ brn/yel screen, brn plate. I connected blue to pin 9 on tube 6973, I connected blu/yel to 8 on same tube, I connected red+ to 12ax7 tube, I connected brn/yel to 8 on other 6973 and brn to 9,  On secondary my schematics on new transformer white 16 ohm, yel 8 ohm, grn 4 ohm blk 0 ohm,   I connected the white to the 16 0hm tap also wired in the orange to same, yel to 8ohm tap green to 2ohm tap there is no 4, and blk to ground.  I started up the unit using dim watt tester, no short , when i tried to play record load hum so i shut it off.  Anyone see anything wrong in wiring.  thanks pete

[jukeboxmarty]

Just clarifying... You connected the red transformer wire to the 12AX7 tube? My schematic is a little hard to read, but it looks like the red wire should go to a point (+375v) in the power supply.

[prime]

My bad , followed the wrong wire, red is going to either c134a or 134b hard to tell ,orange wire tied into 16 ohm is going to 12ax7 tube. everything else is as i stated. I need to look closer before reporting back. If you confirm this sounds right i will restart unit, could be cart or other issue. This unit has never had volume so it may just be a grounding issue

[jukeboxmarty]

It seems correct, but it's hard to tell without being there!

[jukenorman]

If you've got hum or squealing, the transformer is probably wired out of phase. Swap the input wiring.

Norman.

[prime]

Sorry not sure what input wiring is? do you mean swap plate and screen from one tube to the other? I tested output and found 68ohm blue to red, 77ohm brown to red, and no resistance from yellow to blue, i think that confirms its good. this is he output

[jukenorman]

Yes because you have a feedback loop, it all needs to be in phase!

Norman.

[prime]

Hi guys replaced the wires but Norman i didnt explain myself well enough, when i tried to play a record i got loud pops and some kind of hum, i switched wiring same thing so i disconnected the orange wire that used to feed the old output transformer, i now have 60% sound but i still have a hum, can out of phase cause low volume? maybe i am now out of phase. pete

[jukenorman]

According to the drawing, the orange wire provides the feedback, so you definitely need it connected (to the 16ohm wire). I don't think it's possible to draw any valid conclusions based on the info you have given. It's possible to connect the output transformer in the wrong phase but if you do, it squeals/hums badly.

Norman.

[prime]

 For some reason it takes at least 20 seconds from when the needle land on record to hear sound. This has always been the case even with the original transformer. pete  There is some strange issue with the power going to the 6973 tubes  tube 1   pin 1,0v 2,0  3,-34  4,0  5,0  6,-35  7,0  8,405  9,342  Tube 2=  pin 1,428  2,0  3,-34  4,0  5,0  6,,-35  7,37  8,428  9,426   I checked pin 1and 8 on each socket ,tube in and i get continuity on both. how can i get zero on tube 1 when i get 428 on 8 

[jukenorman]

I hate to say this, but are you sure the old transformer was faulty?

Norman.

[prime]

No i see now the old output was fine i will keep it for a spare pete