Sound City 120 Partridge Output Transformer wiring help

[Drewline]

I've got a Sound City 120 amp that had the original output transformer replace with a Fender Twin transformer at some point. The amp's owner brought it to me with a used Partridge output transformer he wants installed in it.
My problem is that I can not find the color code for the secondary leads of this transformer. I have found color codes on the internet but they do not match the wires of this transformer. The amp is marked 4 ohms, 8 ohms, 16 ohms, 100V line.
The painted on numbers are G9909 & TG9375. The colors of the actual wires are: black, yellow, green, brown, blue.
Assuming that black is common, the resistances I get measuring from the black lead are as follows: Green 0.3 ohms, Brown 0.4 ohms, Yellow 0.6 ohms, Blue 2.0 ohms. Am I correct in my thinking that Green would be 4 ohms, brown would be 8ohms, brown would be 16 ohms and blue would be 100V line? Or is there a better way to go about figuring this out?
Thanks in advance for your help!

[g1]

There are only 3 wires on the primary? That TG number is supposed to be for a power transformer.

(edit: seems that TG number appears on both PT's and OT's, so not sure what's going on with that)

[Drewline]

Re: partridge output transformer

There are three wires on the primary. Red, Orange & Black. The secondaries are black, green, brown, yellow, blue.
See photos:

[catalin gramada]

These are the specs of my tranny:

4 ohm - green
8 ohm - brown
16 ohm - yellow
100V - blue
Common - black

[Drewline]

Catalin,
Thanks so much! Is your amp a Sound City 120?

[catalin gramada]

Think it was. I don't remember precisely. I recovered a bunch of good Partridges from SC scrap but had care to carefully notice its specs. What I remember precisely after I did some tests it was this tranny isn't performs perfectly in low freq range, there was made for PA aplication. It run a perfect sine at 120w nominal power at 80 cps. Below this freq it goes in partial saturation for 120w output. Should be well suited for a guitar amp but I.m not as sure for a bass aplication. Cheers.

[catalin gramada]

...Let see the donor...TG9375, right ?




Have some scope screenshots by my tests. You can get 120w at 480V with a quad of EL34.
This trannies runs pretty hot I remember. Don't worry to much, there are very well built transformers.

[g1]

I saw a reference to it also being used in Hiwatt L100 : http://www.diverse.4mg.com/repair2f.htm

"1970 Hiwatt L 100W, 1970
mains Tx TG9743 and G988(6?)
o/p Tx TG9375, G9909
main red caps CCL curley script , philips blue electros & cement cased polyester
Red cap marked Mar 1970, CCL 100uF,70V
Sprague 7001 datecode on 32uF, 450V
o/p Tx 19.9R/17.5R
sig gen reverse test of o/p Tx
1V 100Hz in , 5.41 / 5.41V out , DVM ac monitoring
1V 1K, 5.45/ 5.41
0.8V 10K, 7.53/ 7.51 V ac "

[SoulFetish]

If you're pretty sure you've identified the primary leads, there are a couple of techniques to determine what the output lead orientation is. Assuming you know that you have taps for 4,8, and 16Ω, you can sometimes quickly tell which order - lowest impedance to highest.
If you have an accurate DMM, and you measure the resistance from each lead to common, the lowest impedance lead will have the lowest DC resistance(ie. the 4Ω tap). The 16Ω will have the highest DC resistance, and the 8Ω will be in between the two. This isn't always practical because often all the secondary taps usually look like a dead short across the winding.
But, the other and better way is to inject a signal across the primary, say 10VRMS, you can measure the voltages at each tap to determine what each tap is. If all you need is to identify what color is assigned to what tap, then the 4Ω tap will have the lowest voltage, the 16Ω tap will have the highest voltage, and so on.

[Drewline]

Thanks everyone.

[Drewline]

Partridge T69375/G9909 Output Transformer wiring

Partridge T69375 G9909 OT wiring code.pdf

[catalin gramada]

Actually there are two separate secondaries in parallel think they did it for interleaving reasons .

[Drewline]

You're correct. Each secondary tap is actually two wires.

[vintagekiki]

There are three wires on the primary. Red, Orange & Black. The secondaries are black, green, brown, yellow, blue.

https://www.mercurymagnetics.com/2018/wp-content/uploads/shop/specsheets/HI100-O.pdf

Partridge HI100-O OUTPUT TRANSFORMER
Blue wire is probably 100V line & NFB