CIHFA1 amp replace output transformer

[jukenorman]

20 or 30 seconds is quite a long time, have you looked at the mute contact - is it adjusted correctly and is it clean? That would be the obvious starting point, I would suggest.

Norman.

[prime]

Hi guys last stab at this issue, tube socket voltages retested after reflowing connections 6973
tube 1 tube 2
1 437           1 424          If i need power at tube 1 pin 2 i need to change wiring no connection, also i tested caps at 5y3 c134a 128 c134b 470
2 0               2 -36            c135a 330 c135b 370 c135c 350 c 135d 230. The sound is clear no hum at all just low volume.
3 -34           3 -34
4 0              4 0
5 0             5 0
6 -34          6 -34
7 0             7 0
8 424          8 457
9 423          9 436

[jukenorman]

If you have low volume, the problem could pretty much be anywhere! You would need to inject an audio signal (as described on the schematic) and trace it through to determine where it's failing. Alternatively you could have the amp repaired by a specialist?

Norman.

[jukeboxmarty]

Wow those voltages look much better. Pin 2 does nothing for the output tubes (it's just a tie-point), you can ignore that result. Pins 1 and 8 should yield identical voltages but yours aren't too far off.

Good news that the hum is gone!

Does it still take 20 or more seconds for the sound to come up?

What happens if you pull the 6BJ6 tube?

[prime]

Yes it still takes 20 seconds but i notice when i test one of the 6973 tubes it flickers then slowly shows green with my tester, not sure if that affects the start up, i dont have another 6973 and they are hard to find here at the moment, i do have a few new replacements with different number but i notice on those pin 1 and pin 8 are not connected. I pulled the 6BJ6 no change. Strange it sounds very clear just no volume, I have tested the volume pot a few times and have at least 24600 ohm at full so it should work. I also notice the bass switch offers no change but treble is noticeable. Im thinking of picking up an oscilloscope, do you think that would aid in tracing low volume or not. Lastly can the wrong value on a mylar cause this? I was wondering i tested the wires from the pickup plug to cart and all seems good, While a record playing can i test the plug to see if the signal is strong enough and if so how?  thanks pete

[jukeboxmarty]

You can use the substitute 6973's as long as pins 1 & 8, and 3 & 6 are jumpered on the socket.

I know they are in Arizona, but Antique Electronic supply sells new Electro-Harmonix 6973's. Some people will argue that these tube aren't any good, but I've always had good results with them in Seeburg or Wurlitzer amps.

Also you could try to temporarily remove that pesky orange 'inverse feedback' wire to ensure it's not overly suppressing your audio.

Buying a scope is not a bad idea, but the scope is just a tool... you need to be confident enough about the proper skill set to utilize it.

[spetersen]

The original transformer, if it is good, will always give the best performance. the feedback circuit is tuned for it.