A old one - where to start?

[jeff mills]

I know this was made in 1957 based on Williamson design, there is no preamp and there's about 50 lbs here Can someone tell me what I'm looking at and where to start, it needs to end up as a bass guitar amp

[Gtr_tech]

All those old electrolytics gotta go. After that, check the coupling caps for leakage. Then check all resistors for proper value. Replace any that are too far off spec.

I don't think a pair of 5881s is gonna be much good for bass. Could make a decent guitar amp tho. For bass I wouldn't go with anything less than 4 6L6/EL34. You need the extra headroom or else it will just start sounding dirty.

Looks from yer pix that the pwr supply and amplifier are on 2 seperate chassis? That is limiting. The Partridge output transformer would fetch a decent sum of money if sold to some tube hi-fi nutter. Since its a line input job, its really better suited to hi-fi anyway.

[loudthud]

It's probably not rated more than 25 or 30 Watts.

[jeff mills]

All those old electrolytics gotta go. After that, check the coupling caps for leakage. Then check all resistors for proper value. Replace any that are too far off spec.

I don't think a pair of 5881s is gonna be much good for bass. Could make a decent guitar amp tho. For bass I wouldn't go with anything less than 4 6L6/EL34. You need the extra headroom or else it will just start sounding dirty.

Looks from yer pix that the pwr supply and amplifier are on 2 seperate chassis? That is limiting. The Partridge output transformer would fetch a decent sum of money if sold to some tube hi-fi nutter. Since its a line input job, its really better suited to hi-fi anyway.

Yes the PS has a weird male/female" plug thingy on the end to plug into the amp. It's sounding like the only thing that might be worth while to reuse is the Partridge output transformer, but it's a really a hi-fi type, so possibly not.

[Gtr_tech]

That is a "Jones" connector. Very common at the time.

Yea, I'd just ebay the thing and put "partridge" in the description somewhere. Just that transformer is worth more than 200$.

[Kazooman]

This looks like it could be a very FUN project, but without resulting in much of a useful amp. I have done a few such "restorations" to bring a vintage piece back to life, but I would not sell them for someone to use on a regular basis. Just having fun and enjoying the smell of solder.

If you want to mess with it (cost for new components being no issue) the comments above on caps and resistors are a must as well as checking out both transformers for shorts and continuity. A new three-prong cord is a must. You are going to have to decide on some input / preamp stage for controls and also provide some provisions for the output. (any idea what impedance this OT wants to see?)

If it were up to me. I would try to retain the vintage look of the unit mounting the chassis on some kind of base with some sort of "cage" to protect the other tubes while allowing them to be seen and providing a spot for the controls. I would take a good picture of the cool logo and pull it into Photoshop to digitally repair the blemishes. You could then refinish the paint on the cover and apply a new "vintage" decal.

If you are willing to have a go at this and do not have the means to redo the logo in Photoshop I would be happy to lend you a hand. I would need several IN FOCUS images of the logo along with some accurate measurements. I think that retouching the blemishes should be pretty easy and color decal stock is easy to work with. I can imagine in my mind's eye seeing that housing refinished with a gold "crackle" finish with a sweet "Partridge" logo on the side.

This may be more than you want to take on to get an amp that really won't perform very well. If so, let me know, I might be willing to have a go at it

[jeff mills]

Thanks for all the replies and pointers... Can anyone point me where I could get more information on the partridge? I talked to my buddy who gave me the amp and he told me it's rated for 75 watts, if that's true then I'm seriously considering building a bass amp around it.

I called Hammond yesterday and sent them pictures of the power transformers - they have to go back into their archives to pull up paperwork

[Gtr_tech]

No it ain't. A pair of 5881s is good for around 40w fixed biased. 20-25 cathode biased. You would need a pair of 6550s to get 75w.

[Tom Phillips]

Based on the look of the construction and the lack of markings other than on the transformers your amp/power supply appears to be a home built project. That was a fairly common practice in the 50's. Interesting construction using an eyelet parts board with the tube sockets hard mounted to the board. If you can find a P/N on the output transformer it would sure help the search for information on that unit.

[jeff mills]

No it ain't. A pair of 5881s is good for around 40w fixed biased. 20-25 cathode biased. You would need a pair of 6550s to get 75w.

Thanks Man - yep your right it's got a pair of 5881's, that means 20~25 watt.

[Enzo]

Here is an old Hammond catalog, type 274X is on page 24.

Could that be yours?

http://bunkerofdoom.com/xfm/hammond74/Hammond74.pdf

[jeff mills]

Enzo, I found the choke and power transformers in the Hammond 65 catalog

Power
Choke

Could some one be so kind as to point me to a bass amp schematic that would best utilize the major components (transformers) I already have. I need to decide to convert this into a base amp or give it back to my buddy who gave it to me.

I still would like to find some information on the partridge, but no luck yet.

Thanks

[Ronsonic]

Great vintage hifi piece - mediocre guitar / bass project.

Find a hifi home for it.

My opinion, FWIW.

[Gingertube]

Do you have a part number for the Partridge Output Transformer.
It MAY be listed here under the Partridge General Specs heading
Tubes
There is absolutely NO reason why a HiFi spec'ed Output Tranny can't be used for Guitar Amps.
Hiwatt used Partridge Output Trannies.
Cheers,
Ian

[jeff mills]

I have not taken the partridge out of the case yet to look for part numbers - but I did get an email from Hammond today as I suspected the power and choke trans are confirmed 1950's models as the amp was built in 1957.

I also found a article called The Williams Amplifier - written in 1952 It's a very interesting read, especially when the book starts talking about modifications for "High-Impedance pickups and Long-Playing Records" In the Williamson book there also a Partridge advertisement on page 19.

After doing a little research, I feel I have a tiny piece of history in my hands a 54 year old piece of history.

I still would like to try and find a diagram to build a bass amp around the transformers, I think it would be a fun project... Although not much wattage output, it would still be ok for jamming around the house.