1950s Philco Suitcase Record player Conversion

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captainclock

captainclock

Pacifist Otaku
Hello Everyone,
I have a 1950s vintage Philco Dual Speaker Hifi "Suitcase" Record Player that was given to me as a parts unit (the record player and amplifier still played but the changer didn't work on the turntable anymore and it was missing the cover for the tube access and the grill cloth was shredded).
I was wondering how easy it would be to turn this old Philco Record player's amplifier and case into a practice amplifier for a guitar or bass?
I'm wondering because I got the idea from when I was looking at the wiring that came out of the amplifier (the wire that went to the pickup from the record player) and the wires that went to the power switch/power supply that was integrated into the turntable.

I noticed that it looked like it could be an easy guitar amp conversion but I'm not sure and the power supply wires that went to the amplifier to give it power could be easily integrated into a power switch and a grounded 3 prong cord pretty easily as the power supply wires going to the amp are the typical grounded 3 conductor setup (black, white and green wires).

The amplifier's tube layout is a 50L6 Output Tube, a 35W4 Rectifier tube and a 12AU7 Preamp tube and with that in mind would that be enough to make this into a decent enough practice guitar amp?
I'd be doing this conversion for a friend of mine who would be supplying all the parts that I'd need (switches, 1/4" jacks, power cord, etc.)

So would this be a practical project or is it just a waste of time and money?
 
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Waste of time.
More importantly, electrically unsafe..... and deadly.

Liability suits can be a nasty thing if someone's electrocuted.
 
Alright I guess I might just have to salvage the tubes out of it and just pitch it then because I already gutted the original turntable out of it for parts and not much more can be done with this unit then if that's the case.
 
The output transformer could be used for a single-ended guitar amp. Other than that, not much else. The 12AU7 tube might be worth saving but the other tubes aren't really usable for anything else.
 
nashvillebill said:
The output transformer could be used for a single-ended guitar amp. Other than that, not much else. The 12AU7 tube might be worth saving but the other tubes aren't really usable for anything else.
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I have a 1948 Sparton AM/SW Tabletop Radio that has a 35L6 output Tube in it and I've heard that replaceing the 35L6 output tube in that Sparton Radio with a 50L6 Output tube can effectively increase the lifespan of the rest of the tubes in the radio because it drops the heater voltage slightly, which with the higher line voltages we have now (120 VAC vs. 115 VAC. like what used to be around when the radio was first made) makes the radio tubes work more efficiently.
 
captainclock said:
I have a 1948 Sparton AM/SW Tabletop Radio that has a 35L6 output Tube in it and I've heard that replaceing the 35L6 output tube in that Sparton Radio with a 50L6 Output tube can effectively increase the lifespan of the rest of the tubes in the radio because it drops the heater voltage slightly, which with the higher line voltages we have now (120 VAC vs. 115 VAC. like what used to be around when the radio was first made) makes the radio tubes work more efficiently.
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That Spartan may very well have a power cord with resistance in it...http://www.nostalgiaair.org/References/Articles/TheFlash/Flash01.htm
 
They used resistance line cord up into the late '50's, I believe.

On AA5 radios or other series string radios or record players, the basic premise is that all the tubes will use the same current on each tube heater. Therefore, you can put the filaments in series. The rule for a series circuit--if each device draws the same current--is that the total voltage drop across the circuit will equal the sum of all the individual voltage drops. However, sometimes if you add the heater voltages up, it doesn't total anywhere close to 110 or 115. Let's say you've got a 35Z5 rectifier, a 35L6 power tube, and a 12AX7 preamp tube. That only totals 82 volts. That would work fine if the line voltage was 82 volts...but line voltage is 110 to 120 volts. Connect those heaters in series to 110 volts, too much voltage will go through each heater and tube life will shorten (perhaps dramatically). So the solution was to add an external dropping resistor to drop the extra 30 or 35 volts--that resistor would be sized to draw the same current as the tubes but drop the necessary voltage (V=IR).

However, the radio or record manufacturers were trying to keep manufacturing costs down. Resistors, especially power resistors, cost money, plus they have to be mounted in the radio where they can dissipate the heat. The way to save money? Use a line cord to plug into the wall that had enough resistance to drop the voltage the extra 35 volts. Sure, the line heats up, but the heat is spread out over the length of the power cord. Hey what's a little fire hazard among friends, gotta keep the cost low and profits high!

The RCA book shows a 35L6 and 50L6 both draw 150mA heater current, going up from 35L6 to 50L6 therefore would make sense to drop 15 volts.
 
nashvillebill said:
They used resistance line cord up into the late '50's, I believe.

On AA5 radios or other series string radios or record players, the basic premise is that all the tubes will use the same current on each tube heater. Therefore, you can put the filaments in series. The rule for a series circuit--if each device draws the same current--is that the total voltage drop across the circuit will equal the sum of all the individual voltage drops. However, sometimes if you add the heater voltages up, it doesn't total anywhere close to 110 or 115. Let's say you've got a 35Z5 rectifier, a 35L6 power tube, and a 12AX7 preamp tube. That only totals 82 volts. That would work fine if the line voltage was 82 volts...but line voltage is 110 to 120 volts. Connect those heaters in series to 110 volts, too much voltage will go through each heater and tube life will shorten (perhaps dramatically). So the solution was to add an external dropping resistor to drop the extra 30 or 35 volts--that resistor would be sized to draw the same current as the tubes but drop the necessary voltage (V=IR).

However, the radio or record manufacturers were trying to keep manufacturing costs down. Resistors, especially power resistors, cost money, plus they have to be mounted in the radio where they can dissipate the heat. The way to save money? Use a line cord to plug into the wall that had enough resistance to drop the voltage the extra 35 volts. Sure, the line heats up, but the heat is spread out over the length of the power cord. Hey what's a little fire hazard among friends, gotta keep the cost low and profits high!

The RCA book shows a 35L6 and 50L6 both draw 150mA heater current, going up from 35L6 to 50L6 therefore would make sense to drop 15 volts.
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The Sparton Radio is an AA6 Radio (it has 6 tubes not 5) and I have never experienced the cord getting extremely hot, The tube lineup in the radio is as follows:

12SK7GT
12SA7GT
12SK7GT
12SQ7GT
35L6GT
35Z5GT

Which the voltages from those tubes all add up to 118 Volts exactly.
I just figured out that with a 50L6GT tube in place of the 35L6GT it would bring the voltage of the tubes/radio up to 133 Volts (I measured the voltage at my outlets in my room at about 122 Volts) which is an 11 volt difference.

I would say that the tubes might still be worth saving because I do work on radios for people and I might be able to have the tubes as spares for working on someone elses radio that might use a 50L6GT tube.

The 35W4 tube is what my old Zenith Radio uses as its rectifier tube so I would have that as a spare and same for the 12AU7 I could use it in my old Columbia Stereo Record Player in place of the 12AX7 in there in case I need to make a subsititute.
 
nashvillebill said:
Doesn't appear you have anything to worry about then, sorry to muddy the water with the line cord possibility.
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Its fine, nothing to worry about. :)
Its just that I've noticed that quite a few people for some reason have mistaken my Sparton Radio for a 5-tube Radio for some reason, it was the same way on another forum I was on previously before I joined this site.
Anyways enough of that for now, I guess I'll just salvage the tubes and what not and just chalk it up to a learning experience.
 
Correct me if I am wrong, but it seems to me that you're taking on a whole lot of projects at one time with essentially no experience. You might want to pick one and work on that and leave the others be for a bit. Just a thought.
 
Wigwam Jones said:
Correct me if I am wrong, but it seems to me that you're taking on a whole lot of projects at one time with essentially no experience. You might want to pick one and work on that and leave the others be for a bit. Just a thought.
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Well actully I do have some experience, I have already recapped several radios already within the past few years and I've also even repaired several old VCRs, TVs, Stereo Receivers (mostly of the old boombox persuasion), tape players, record players, 8-track players etc.

The Magnavox Console I mentioned in a previous thread is supposed to be a long term project, the Sparton Radio I had mentioned in this thread I had already repaired, and then I'm working on an old RCA 45 RPM Record Player for a guy (he's supposed to be paying me any money I would need for any parts I would need), and I'm also working on an old Arvin AM/FM HiFi Radio for another guy and both projects are being held off until I can get the money for the rest of the parts (the Arvin just needs two more electrolytic caps and it will be all set to go).
 
century tek said:
Captainclock, I think others here including myself are just using the AA5 as a reference to series string radios. They made many series string radios and amplifiers that used more than 5 tubes but the AA5 was the most manufactured so that is why people have mentioned it here even when talking about your Zenith or Sparton radio so please don't think we're saying your Zenith is an AA5 radio.

TV's of the power transformerless era used 15 to 20 tubes all in a string. These sets had tubes in them with different heater voltages such as 4, 5, 8, 9, 15........you get the idea.

http://en.wikipedia.org/wiki/All_American_Five
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Well My zenith I have has 9 tubes in it and its from the early to mid 1960s so it would of been after the time period of the AA5 radios (it has a transformer in it with the safety interlock type powercord which was the radio industry's answer to fixing the "hot chassis" issue.
Its the same deal with this mid 1960s vintage Arvin Radio I'm working on it too has a transformer with a safety interlock power supply.
As for the Sparton Radio there was an AA6 type of radio which was a little different than the AA5 radios because traditionally speaking an AA5 radio only has 5 tubes in it and an AA6 radio traditionally speaking has only 6 tubes in it, it has nothing to do with how its wired because you have a 5 or 6 tube radio and it could be parallel wired and it would still be technically an AA5 or an AA6 radio same goes for the 10 or 15 tubed radios but they don't necessarily give the radios with more than 6 tubes a designation because it would be a bit redundant (same for radios that have less than 5 tubes).
 
century tek said:
This doesn't make any sense. You can't parallel wire an AA5. There's no way! The AA5 was a series string tube radio with no power transformer. A speaker transformer yes, but no power transformer.



Did you not read that wiki link?

I own a 20 tube color TV which is a hot chassis TV because it has no power transformer. If it did, all the tubes heaters would be wired in parallel and the tubes would all have numbers starting with 6. This TV has no tubes starting with the number 6. It also has an interlock to prevent electric shock but that doesn't mean that it is not a hot chassis.

Your Zenith is not a hot chassis radio if it has a power transformer and the tubes have numbers starting with 6.

You're not getting my earlier meaning but that's ok as I probably didn't explain it quite right!
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I DID read the wiki and they DID have parallel wired 5 and 6 tube radios, they were known as "farm radios" or radios that ran strictly off of 32 volts DC Windmill power and those radios were indeed parallel wired, go back and read the wiki again, also they did have AA5 radios with Transformers as well, (also also mentioned in the wiki and they were parallel wired as well) also your battery powered or 3-way powered radios also were parallel wired (also mentioned in the wiki) I think you need to go back and reread the wiki seeing as it seems that you didn't completely read the wiki.

And please don't take what I'm saying personally but it just kind of annoys the heck out of me when people assume I didn't read up on anything when in fact I did and I wouldn't just make stuff up just for the heck of it, I'm not that stupid.
 
Pio1980 said:
Line cord resistors were also known as "curtain burners" for reasons that should be obvious if anything went wrong, they rather rapidly went out of use AFAIK by the late 1930s for other options like large wirewound resistors and using the phono motor as a heater supply auto-transformer. The output tube option could also be called on as per 25L6, 35L6, 50L6, ect. The ubiquitous Motorola entry-level ($199.95) electrostatic 7" and 8" televisions of the late 1940s used multi-section resistive ballast devices to get the tube cathode heater power requirements sorted out without the need for a costlier and heavier power transformer. A dual selenium rectifier doubler provided the other working DC voltages, and FWIW, one of the first commercial applications for the "new" 1N34 germanium diode was as the video IF signal detector.
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Agreed, I was figuring that radios wouldn't of had resistance cords on them by the 1940s but there were a couple of people on here that seemed to think otherwise (including someone over at another antique radio forum that wrote a whole article about them and claimed that they were used up until the 1950s). Anyways I don't want to make a whole arguement about this subject so we'll just leave it at that. :)
 
Also I had said I was giving up on the idea of converting this old philco record player into a guitar amp.

So how did we get from discussing the conversion of an old record player amp into a guitar amp, to discussing old radios and how they work?
The way I see it this thread somehow got way off subject.
I think we just need to abandon this thread and move onto something else before things get too out of hand.
Agreed?
 
century tek said:
I have read it a thousand times and know all about them! I am also a 40 year repair tech. You still didn't get my whole meaning of hot chassis so good luck with your endeavors.
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And apparently you never read any of my posts where I said I had given up on the idea of converting this record player amp into a guitar amp!

Also where do you get off trying to throw this whole topic of discussion off subject by trying to question my knowledge of vintage electronic repair?!

I told you (and everyone else here) that this topic wasn't up for discussion anymore and that it needed to be dropped.
But apparently you didn't get that message (it was the message right before your post).
So I'd appreciate it if we'd just respect each other's differences in opinions concerning these matters and just drop this discussion before it gets too far out of hand.

Kapiche?
 
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120 volt isolation transformers are on ebay for 20 bucks,
there ended the unsafe chassis claims

They have been made into low power guitar and harp amps do a google search.

besides I have many non transformers radios and even a 50c5 RCA stereo amp. People lived with them for 30 years
 
jsixis said:
120 volt isolation transformers are on ebay for 20 bucks,
there ended the unsafe chassis claims

They have been made into low power guitar and harp amps do a google search.

besides I have many non transformers radios and even a 50c5 RCA stereo amp. People lived with them for 30 years
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I wasn't trying to sound mean or rude, but I was just trying to mostly get this back on topic, because it had somehow gotten way off topic and I quite frankly was too generous by letting it stay this far off topic for as long as I did which is why I'm now cracking down on the situation like I am.

Anyways I appreciate your advice, and I definitely had been looking into the isolation transformers since I had heard about the "hot chassis" issue with this record player amp, because it was actually suggested by some other members on here too but they were saying that even though it could be done it might not be worth it because of how its setup.

Which is why I had kind of swayed away from the idea for a bit, because I didn't really have enough feedback to really convince me either way whether or not it would be a good or bad idea to do this conversion because most of the comments I was getting were mostly negative comments which isn't enough to determine either way because I also wanted to hear from the other side as well.
 
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