Picked up a couple of new pieces to restore

A Sparton model 7-46PA Monaural Phono and Tuner console. Looks like a field coil 12". It uses Loctal RF and preamp tubes and PP 6F6/6V6 with 5Y3 rectifier. It appears to be WWII vintage with a later replacement VOM TT. So far I really like this piece and want to make it my beside system. The TT is in a drawer with only a small access from the top for the pretty little tuner/control center so it can double as a nightstand.





Bet she was a pretty girl in her day.



I like the wooden knobs.



http://www.audiokarma.org/forums/attachment.php?attachmentid=146295&stc=1&d=1239925463

That loop antenna looks like it is intended that you would be able to swivel it for best reception but it only moves an inch or so before it runs into either the speaker coil or the storage space.

mike

A closer look at the OPT and speaker.



The turntable installed does not match the one described in the owner manual in that it is multi-speed (rather than 78 only) and uses a rotary control for starting and stopping rather than the linear slider described in the manual.



Lots of scratches. I hope that they can be repaired without destroying the rest of the finish.

mike

GE stereo console

The second unit is a more pedestrian GE stereo console.





Unlike my RCA console this one has a stereo tuner. I don't have a schematic yet so I don't know how promising the tuner might be but...



The tube map may provide some clues.



The 8" mid/woofs look interesting, might be OK. Looks like a Selsun Blue rectifier there to replace.



6AQ5 SE outputs. I suspect pentode mode.

The users manual covers models RC4151B, RC4152B, and RC4155B but I can find nothing online about any of them.

Saturday I go back and pick up a Hammond Spinet tube organ. May be a tone-wheel model as there are oiling instructions on the back. It has both tabs and draw bars. I don't know model number or if it is valuable but there is glass in there so must be good huh?

mike

No extra charge for the spiders...

Wanted you to see her in all of her unrestored glory. Actually there was no charge at all.

mike

Very nice! That Spartan would be great as a musical nightstand! The Field coil speakers tend to sound nice as well :thmbsp:

Is the top on the first one solid wood or veneer? Book ended wood furniture from that era can look real nice when refinished. I've got a couple nice dresser drawers. I'd just strip it, sand it with 120 or even lighter and then put a natural tung oil or some other clear oil on it.

Lar

I think it is solid wood but looking at some of that figuring I wonder. I will take a close look tomorrow.

mikw

mashaffer said:

I think it is solid wood but looking at some of that figuring I wonder. I will take a close look tomorrow.

mikw

Click to expand...

Looking at the close up it sure looks like solid wood, the color of the edge grain matches the color on top. I've seen other pieces of that era where the top is the only solid piece with veneered used on all the rest. That wood sure be a bonus. :yes:

Lar

Dig this crazy output stage.



I am still trying to grock this out fully but it looks like the signal modulated onto the screen dropping resistor of the upper tube provides the inverted signal for the bottom tube (which strangely has no dropping resistor). I am not sure if the pot and caps at the plate of the top tube provides adjustment of the relative gains or not. It is kind of a strange lash up no? It does manage to provide inversion with almost no extra parts.

mike

mashaffer said:

Dig this crazy output stage.


I am still trying to grock this out fully but it looks like the signal modulated onto the screen dropping resistor of the upper tube provides the inverted signal for the bottom tube (which strangely has no dropping resistor). I am not sure if the pot and caps at the plate of the top tube provides adjustment of the relative gains or not. It is kind of a strange lash up no? It does manage to provide inversion with almost no extra parts.

mike

Click to expand...

Do you have the rest of that schematic? I have a 1940 GE floor radio that had a seemingly complicated output stage, but it was due to the hard to follow schematic. It turned out to be a standard paraphase stage that one half of a 6SK7 was used for signal rectification, while the other was used as the top driver, and the phase inverter was a separate 6J5 tube. The output transformer is normal, but since it uses an electrodynamic speaker with a field coil, it has a hum-bucking coil(sometimes called a hum-neuter coil) built in to try to reduce mains hum caused by either the electromagnet or cutting costs in the power supply.

I have however seen one old valco amplifier that I can think of that uses the screens of the 6v6's to transfer signal and the input grid of the bottom 6v6 only has a 470k resistor to ground and is not fed with any signal. I think power output is about 10 watts, but probably less since that is not a very efficient way of doing things.

I traced your circuit, and it does indeed appear to have the latter arrangement- a self split type output stage. Here is a good example:

I have attached the entire schematic package in PDF for your enjoyment.



This looks to me like a solid piece of wood on top with a thickish veneer on top of that. The side panels look like thin plywood over solid wood. I suppose this allows cheaper wood for the bulk of the structure with a nicer finish. This might be tricky enough to warrant a professional huh?

mike

As I look more closely at speakerdude's schematic they are about the same. I guess that the resistor in the Sparton's resistive pi filter (the one right after the CLC filter made from the speaker field coil) is what is intended to limit the screen current on the bottom tube.

mike

And here is the last piece. Hammond L-101.





It has the tonewheel generation system but it seems to be mounted with only rubber grommets rather than a spring suspension.



It has two 12" drivers



and a sweet looking little 6BQ5 PP amp with a pair of Amperex 6BQ5s, a pair of Hammond 12AX7s, a Hammond 12BH7A, and a 5U4 regulator.



mike

Nice machines!! Best of luck with the restorations!

Saw a Hammond organ very similar to this one at the SA up the street. It was priced at $500.00! Went back a couple days ago to check on it and it was gone. I asked the guy on the floor about it, he said they had to throw it out because of some bad wiring! A day late and a dollar short. The amp looked very similar, I just could'nt stick my head in far enough to get any details, nice grab, looks like some serious iron.

I am actually seriously considering refurbishing the workings and then if I like it giving it a chop job. (http://en.wikipedia.org/wiki/Hammond_organ#Chop_organ) I figure most of what I invest in getting it up to speed would still be useful if I eventually decide to use it as a donor.

mike

Well I jumped into the Sparton the other day. This just gets more and more interesting. It is becoming clear that this thing has been highly modified by a previous owner. In some ways it was quite cleanly done while in other ways is quite amateurish. Fortunately none of it is buggered in ways that are visible or hard to remedy.

My first clue was the owners pamphlet which constantly referred to the controls in terms of left and right while my unit has controls oriented front to back. The manual also indicated that it came with a 10" speaker while the one install was clearly a 12" model. Couple that with the fact the the loop antenna could not be rotated as it was obviously intended to.

An auction on the Italian eBay site for the SAMS folder for this unit clearly showed a picture of a classic stand up radio with horizontal (left to right) control orientation. So some PO apparently chopped the top off when they added the 60s vintage record changer. The exterior of the TT drawer is quite nicely done and the mounting of the TT looks fine but the access hole in the bottom of the drawer is crudely hacked out.

When I removed the speaker I found that the new 12" driver was just screwed into the fiberboard baffle with the 10" hole unchanged. There is also no dust cap on the speaker so hopefully the fluff from the disintegrating baffle board didn't get in there to gunk things up as it looks like a pretty nice driver otherwise. Also note the glue that was allowed to drip on the cone.



Clearly the cardboard sided record storage cubby holes were added with the chop job as the right side one was interfering with the antenna. I intend to shorten that one enough to allow the antenna to swing properly. Hopefully if I make the new baffle board with the driver mounting as far left as possible I will be able to get the antenna swinging freely.

The rust on the speaker electromagnet and the condition of the baffle board indicate that it has been stored in some damp conditions.



The amp itself doesn't look too bad and was apparently working fine until there was a loud pop and the unit quit working.



My hope was that the caps in the RF and IF section would be of the long lived ceramic type like most other old radios I have seen. When I exposed the guts however it is almost all paper caps except for a few micas so it may be very difficult to avoid the necessity for a realignment. Unfortunately I have neither a scope or an RF generator so that could be an interesting problem.



I am not yet sure but it looks like those square metal things with screws in the middle of them might be variable capacitors which might be involved in the alignment process so if it turns out that these and the micas are the only ones in the RF and IF section then it might not be all that bad.

Here is a close up of one of the paper caps. As you can see it is kind of gunky and darkened. I don't know if that is from overheating, dampness or just ooze. In any case I plan to replace the can cap and all paper caps as a minimum. I suspect that most if not all of those CC resistors will be on the chopping block as well.



Well in any case a big job is ahead but I think it is worth it. However, given the amount of work ahead I will probably let this one simmer for a little bit while I finish my crossover amp.

mike

Try some of this stuff http://www.kramerize.com/ on th Sparton cabinet. While it won't remove the scratches it will make them somewhat less visible and will revive the original finish. I've used it several times on old finishes with excellent results.