Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: matt mincer on May 20, 2017, 05:49:54 pm

Title: Cordovox
Post by: matt mincer on May 20, 2017, 05:49:54 pm

Hey All,

Today I bought a 2 part Cordovox accordion amp and tone generator box. The plan is to convert the amp into a guitar amp and use the 2nd cabinet for an amp I have already built. Anyone know where I can find the schematic for this? 

Thanks
Matt

Title: Re: Cordovox
Post by: Ritchie200 on May 20, 2017, 10:16:28 pm

Matt,

Did you happen to see this project?

http://www.chosenfool.com/?p=146 (http://www.chosenfool.com/?p=146)

Jim

Title: Re: Cordovox
Post by: kagliostro on May 21, 2017, 06:57:24 am

Matt Mincer do you have an exact model for it ?

Franco

Title: Re: Cordovox
Post by: matt mincer on May 21, 2017, 09:26:50 am

Jim,

I did see that posting. He couldn't find a schismatic either. There's a tube chart on the inside but no schematic anywhere. The post will give me a good jumping off point.

Franko,

Take a look at the attached pic. The only model is Cordovox. Weird!

Thanks to both of you.

Peace
Matt

Title: Re: Cordovox
Post by: sluckey on May 21, 2017, 11:11:27 am

A google search turned up a site that has service manuals for sale. The link was near the top of my search.

Title: Re: Cordovox
Post by: Tony Bones on May 21, 2017, 12:06:46 pm

It's probably not a very complicated circuit,(though it might have some features that looks funny if you've mostly only looked at Fender schematics.)

Have you considered trying to trace out a schematic yourself? There's no better way to become familiar with what's in front of you.

Title: Re: Cordovox
Post by: matt mincer on May 21, 2017, 01:03:43 pm

Yeah, once I got the chassis out of the cabinet, I realized how simple it is. It's only got a 12AX7 phase inverter and 2 power tubes. Most of the circuitry, including the preamp is in the tone box. Should be an easy conversion. Plenty of room to work.

Thanks
Matt

Title: Re: Cordovox
Post by: matt mincer on May 21, 2017, 03:50:02 pm

Here's a look inside

Title: Re: Cordovox
Post by: PRR on May 21, 2017, 03:51:55 pm

Historic fluff: "Chicago Musical Instrument Company" was better known as CMI, controlled Gibson for a while, merged into Norlin later.
https://en.wikipedia.org/wiki/Chicago_Musical_Instruments

Can't imagine the power amp circuit is much of a puzzle. The tone-generator needs an organ guru, but is of little interest without the wired accordion.

Title: Re: Cordovox
Post by: sluckey on May 21, 2017, 04:12:59 pm

I don't see an output transformer. Is it mounted on a speaker?

Title: Re: Cordovox
Post by: matt mincer on May 21, 2017, 04:39:15 pm

Here's a top view. Check out the size of the power transformer. The sockets on the right (or middle) are plugs that attach to the wire to connect the two halves.

Title: Re: Cordovox
Post by: sluckey on May 21, 2017, 05:12:12 pm

Ah, it was hiding in plain view.  :icon_biggrin: That PT is so big because it probably powers all those tubes on the generator chassis.

Title: Re: Cordovox
Post by: matt mincer on May 21, 2017, 05:57:05 pm

Yeah, it does drive them all. It's wild because the power comes into this chassis, goes through the cable to the 2nd box and to a power switch, then back to here to be stepped up and rectified then back to the 2nd box, B+, 6V and all to power 60 plus tubes, then finally the signal comes back to here for the final stage of amplification.

M

Title: Re: Cordovox
Post by: PRR on May 21, 2017, 08:33:01 pm

It smells like a 40W amp (two 7591).

The OT is small, small enuff to screw to the top, because an accordion has no bass (apparently not even with a tone-organ attached).