Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: B-Rex on December 22, 2024, 08:50:56 pm

Title: Output Transformer Help Please
Post by: B-Rex on December 22, 2024, 08:50:56 pm
I'm working on a Robinette JCM 800 build with with the option for 6V6, 5881, 6L6 and EL34. The design uses two output jacks (8 & 16Ohm) to adjust for the different output tubes.

I'm trying to salvage parts from an 67 Ampeg GoldenGlo III and the output transformer has 2 green and 2 black leads. When paired black to green both are reading .5 which would have to be 8 Ohm considering the original amp.

Can these be wired for 8 & 16 Ohm output jacks?
Title: Re: Output Transformer Help Please
Post by: SEL49 on December 22, 2024, 09:31:19 pm
Can these be wired for 8 & 16 Ohm output jacks?
No. The two greens are tied together, and the two blacks are tied together. There is only one 8Ω secondary winding and no taps. Looks like this...
Title: Re: Output Transformer Help Please
Post by: pdf64 on December 23, 2024, 04:21:55 am
What's the resistance between the green wires, and between the black wires?
Probably either a short or open circuit.
Title: Re: Output Transformer Help Please
Post by: B-Rex on December 23, 2024, 06:03:06 am
Green and black pairs are both reading about 0, open I guess?

Thanks for the responses!
Title: Re: Output Transformer Help Please
Post by: pdf64 on December 23, 2024, 07:36:03 am
Green and black pairs are both reading about 0, open I guess?

Thanks for the responses!
What does your meter read when the probe tips touch together?
What does it read when attempting to measure the resistance of fresh air?
Title: Re: Output Transformer Help Please
Post by: B-Rex on December 23, 2024, 01:38:41 pm
There is no reading without some contact. The leads together are similar to the green and black pairs - drifting a little around 0
Title: Re: Output Transformer Help Please
Post by: HotBluePlates on December 23, 2024, 05:56:19 pm
Green and black pairs are both reading about 0, open I guess?
What does your meter read when the probe tips touch together?
What does it read when attempting to measure the resistance of fresh air?
There is no reading without some contact. The leads together are similar to the green and black pairs - drifting a little around 0

pdf64 was trying to get you to notice for yourself that the two Gren wires must be connected (Zero ohms), and the two Black wires must be connected (Zero ohms).  Whether or not you connect them externally, they are still connected internally.

This is not a multi-tap output transformer:  8Ω only.