Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: mresistor on January 28, 2021, 02:53:10 pm

Title: AB165 Bassman Output transformer identification help
Post by: mresistor on January 28, 2021, 02:53:10 pm

Got an AB165 on the bench. Funny though this one has an OT with two output impedances.  Has Black -Green- Green/Yellow wires.
Part number is 021009 and it was made in 1964.   


I've looked around the net and can't find anything on this one.
Anyone have any info on it?  It's a brute.


Thanks

Title: Re: AB165 Bassman Output transformer identification help
Post by: tubeswell on January 28, 2021, 03:56:07 pm

I would say its a 60W OT with 4k2 Pr and 4R and 8R secondaries. Yellow and Green are the 60s Fender OT wire colours for 4 and 8 respectively, and if it looks bigger than 40W, its probably 60W. Classic Tone has a possible replacement candidate http://www.classictone.net/40-18008.pdf If it measures the same size as that, its what it could be. YMMV

Title: Re: AB165 Bassman Output transformer identification help
Post by: mresistor on January 28, 2021, 05:17:03 pm

Thanks Tubeswell - I did see that CT OT 50/60W and was thinking this one is similar but this one is 3.75" x 3.75" x 3.5"H.   The one output wire is green with a yellow stripe.   
I guess it might be an original transformer just not sure.

Title: Re: AB165 Bassman Output transformer identification help
Post by: tubeswell on January 28, 2021, 05:40:13 pm

Quote from: mresistor on January 28, 2021, 05:17:03 pm

Thanks Tubeswell - I did see that CT OT 50/60W and was thinking this one is similar but this one is 3.75" x 3.75" x 3.5"H.   The one output wire is green with a yellow stripe.   
I guess it might be an original transformer just not sure.

Might be 100W OT then - Is there a Fender date code on it?

Title: Re: AB165 Bassman Output transformer identification help
Post by: mresistor on January 28, 2021, 05:50:42 pm

yes  066 412

Title: Re: AB165 Bassman Output transformer identification help
Post by: mresistor on January 28, 2021, 05:52:40 pm

I was thinking it might be a 100w OT  as it almost doesn't fit in the alloted space on this 65 bassman.  So I'm wondering if the input is for 4x 6L6 or 2x 6L6 ?

Title: Re: AB165 Bassman Output transformer identification help
Post by: tubeswell on January 28, 2021, 05:56:20 pm

Depends what speakers that whoever did the conversion were running with it. The aim for 2 x 6L6GC is 4k (or 4k2) plate-to-plate.


You could put 5 or 6VAC on each of the secondaries and see what you got on the primary (disconnect the CT from the reservoir cap first)

Title: Re: AB165 Bassman Output transformer identification help
Post by: mresistor on January 28, 2021, 06:03:24 pm

Right I was just thinking Im going to have to check this one out electrically ..     I'll get to it tomorrow.   Thanks for the assistance.

Title: Re: AB165 Bassman Output transformer identification help
Post by: 2deaf on January 28, 2021, 06:16:41 pm

It's a Twin Reverb II OT.

4-6L6

105W

GRN/YEL  4 ohms

GRN  8 ohms

Manufactured in the 12th week of 1984

Title: Re: AB165 Bassman Output transformer identification help
Post by: mresistor on January 28, 2021, 08:21:47 pm

Thank you 2 Deaf..   so we will be getting a new Mercury OT for this amp.  I see that now in the Schematics index.    cool..   again  thanks .

Title: Re: AB165 Bassman Output transformer identification help
Post by: J Fletcher on January 29, 2021, 12:51:08 pm

 That's a pretty good transformer , though in a Bassman the best speaker load would now be 8 ohms or 16 ohms , depending on which tap is used. Lots of people are running these amps in 8 ohm enclsures . Just sayin' FWIW .

Title: Re: AB165 Bassman Output transformer identification help
Post by: mresistor on January 29, 2021, 05:30:59 pm

Thanks J   - actually I found a Classic Tone 40-18001 OT for sale..    they are good as I have one in my Super Reverb..   so   we are going with that option and a three way switch in the ext speaker hole.
My SR is a Hoffman boarded head. 
 

Title: Re: AB165 Bassman Output transformer identification help
Post by: HotBluePlates on January 30, 2021, 03:29:14 pm

Quote from: mresistor on January 28, 2021, 02:53:10 pm

Part number is 021009 and it was made in 1964.   

Quote from: 2deaf on January 28, 2021, 06:16:41 pm

It's a Twin Reverb II OT.
...
Manufactured in the 12th week of 1984

It's worth knowing Fender used "125___" part numbers (like "125A13A") until sometime near early-mid 1966.  Then they switched to the 6-digit "022____" part numbers.  021___ and part numbers with a letter prefix came in later, sometime in the 70s.

Title: Re: AB165 Bassman Output transformer identification help
Post by: mresistor on January 31, 2021, 10:37:36 am

Thank you for that info HPB .