Mandolin Arm Rest

Here's another small project.  I made a Mandolin arm rest from some wood I had laying around and a violin chin rest from a local music store.  I cut the wood to match the curve of the mandolin and then started carving.  I stained it with the leftover stain from when I refurbished the mandolin so that they closely match.  A final french polish to finish it off.

Webcor Amp Conversion III

I'm done for now.  Everything works great and sounds good too.  There are tons of things that could have been done but this was strictly to get something running without completely rebuilding the thing...

Webcor Amp Conversion II

I did a little more work on the amp the other day.  I picked up some sample fabric from a local fabric store  that just happened to be big enough to cover the new baffle I made for the amp.  I have swapped out the speaker from the Conn organ and replaced it with a JBL D-123 from the mid 1960's.  The JBL is a much beefier speaker.

I've got a few things to finish up on this amp.  I don't want to do too much modifying.  This was supposed to be the simple one.  I have plenty of parts to make a more complicated amp later.

What remains to be done:

Fuse Block
Stand-by Switch
External Speaker Jack
Power Light
Remote mounting of "Gain" potentiometer
Add in a "Master Volume" potentiometer between the preamp stage and the Power amp.

Here are the most recent pictures:

Webcor Reel-to-reel Amp Conversion

I purchased a 1950's Webcor reel-to-reel tape recorder last week ($15).  It has two units to it, the main unit and an extension speaker.  Both have tube amps in them.  I've decided to take the extension speaker and turn it in to a tube guitar amp.  Basically, I didn't want to rewire the whole thing so I thought it would be cool to leave it unmodified for the most part.

The extension speaker by itself has two 12AB5 tubes in a push-pull setup and one 12AX7 preamp tube.  I was able to hook my electric mandolin in to it and test it without modification.  The issue is that there just isn't enough gain doing it this way.  Upon further examination of the schematics, turns out there is a separate preamp in the main unit for this extension speaker.  So, the plan here is to move the preamp over to this box.  From what I've read, this amp should be about 10 watts.

The original speakers consisted of three speakers for full range.  I made a new front baffle as to not modify the original box, added a 12" speaker from an old 1970's Conn organ I stripped for parts, added a couple of component plates for input and volume.  By placing new components on the new baffle, the enclosure can be unmodified and retain its original look.

I did modify the original input plate with a new plug and a power switch.  I need yet to add a fuse block to fully protect it.


Original and unmodified:

 

The new version:

I was not able to test it by the time I powered it up (too late in the evening).  I'll try it out tonight...

The other part of the reel-to-reel I'll strip down and use the components to wire a guitar amp from scratch.  By doing this, I can add a tone stack, over drive control of the preamp, effect loop, external speaker jacks, line out, reverb, and other various options.  There are hundreds of schematics out on the internet.

Truetone D-696 - Detrola 175E

I fired up the radio over the weekend.  Much to my surprise, the motorized preset tuning works great.  It seems that one tube is bad but everything else seems okay.  I'll be trying to find a replacement tube shortly.  There's a bit of hum but that could be the bad tube or it could be that some capacitors need replaced.  I'll see what it's like after the tube is replaced.

Truetone D-696 - Detrola 175E

Here's a few shots of the latest cabinet refinishing work on the radio.

 

  

Variac

I mentioned in one of my previous posts that I purchased several variacs to use in testing and gently bringing up all of these old tube amplifiers.  I made an enclosure for one of them out of an old UPS that had bit the dust.  Here's how it turned out...