[Marsupial]

When I restored my 47-1230 years ago, the record changer on it was in very bad shape. Motor seized, cartridge damaged. Plus - I own 33 and 45 rpm records, but no 78.

I gifted the record changer to another phorum member who needed the same model and wanted to tackle the project. Shipped in a foamed box. Included the matching transformer with it. 

A few years later I bought a voice of music vm-1200a as a period correct "upgrade" for the machine

It works well but isn't loud. 

Should it be using the (now missing) matching transformer?

[MrFixr55]

Hi Marsupial,

The turntable that you removed has a magnetic cartridge. Does the new turntable have a magnetic or ceramic cartridge? 

Magnetic cartridges needed more amplification but generally had much less distortion than ceramic pickups and much, much less than crystal pickups.

I don't think that the transformer is the issue.  This set has a "Phono Preamp" stage that is needed for magnetic pickups but would not be used for a crystal or ceramic pickup.  You may be overdriving this preamp, as there is no volume control for it.  The phono connects directly to this preamp stage.  The output of the stage goes to the radio / phono switch.

You may want to eliminate this stage and connect a jack to the radio-phone switch phono circuit instead of the preamp.  See the schematic below:  If you had a magnetic cartridge (GE RPX, Shure M3D or M7D wired for mono, etc.), then you would use the preamp stage.

Check the turntable on another amp to verify that the cartridge is good.  Is this a mono cartridge (2 leads)?  If this is a stereo cartridge, make sure that you have it phased correctly.  Reversing one channel will attenuate the output unless you were playing Edison records.

Attached below is a partial schematic that I marked up for clarity (or confusion):

Philco 47-1230 Audio Stage, Phono Preamp.pdf Size: 272.33 KB  Downloads: 124

[Marsupial]

Thanks MrFixr55.

The vm-1200a has a ceramic cartridge.
It is mono, to match the 47-1230 that is also mono - it is partly why I chose that phono.

The signal it outputs is too quiet for the radio preamp stage (that has no settings as you said) but the sound is clear.
It's just too low.
Like... About half the volume of the radios.
I need to crank the radio volume to max to get something suitable to listen.

At some point I had made a preamp with a amp-on-a-chip - and it worked, even remained somewhat clear unless I cranked it very high - but I dislike using microchips to increase the signal into a tube preamp. Feels wrong.

I am thinking a suitable step-up transformer could do the trick without adding transistor era to the signal.

[MrFixr55]

Hi Marsupial,

I am scratching my head here. I Although only a hobbyist, I am a 70 year old hobbyist and have been fixing and experimenting with electronics since I was 10. years old, even fixing phonographs for my Catholic elementary school in 5th grade when my older sister told her 8th grade teacher that I co0uld fix the classroom phono, which was older than me. I have fixed many a 1950s record player in my day. The average phono amp for a monaural ceramic cartridge consisted of one triode audio voltage amp and a pentode output. In other words, a 12SQ7, 50L6 and 35Z5 or 12AV6, 50C5 and 35W4; the amplifier and power section of an AA5 radio. For more power, a triode 1st audio, a phase inverter and 2 pentode outputs in push-pull, exactly like your radio. Many a phono with a crystal cartridge did not even have the triode 1st AF amp. They consisted of a selenium rectifier and a 50L6 with the heater in series with the motor which had a 70V rating.

Ceramic cartridges generally had an output of approximately 0.5V. Crystal cartridges had outputs as high as 3V. Magnetic cartridges had an output of 0.005 - 0.10V. This is why your radio has the phono preamp stage. A ceramic cartridge connected to this preamp should drive the amp into distortion.

My guess here is that either the cartridge is good and the phono preamp is bad, or (more likely) the phono preamp is good and the cartridge is bad. However, it is rare that one triode in a tube goes bad and the other is good. Ceramic and crystal cartridges do go bad and the turntable you have is 70 years old. My semi-educated guess is that the cartridge is bad.

If you have a HiFi or stereo amp, plug the turntable output into the aux input (not the phono input unless the phono input had a "ceramic" setting), and test for proper output.

Alternatively, if the radio plays loud and proud, then disconnect the connection from the phono preamp to the radio / phono switch, add an RCA jack and plug your audio from the turntable there and see how you fare. If the sound is lower than the preamp, then the cartridge is bad.

You should not need a transformer. The transformer was an impedance matching device to match the low impedance of the magnetic cartridge to the high impedance input. I have never seen a matching transformer used with a ceramic cartridge. In fact, I have never seen a matching transformer with a magnetic cartridge made since 1949. I have had turntables using the GE RPX cartridge lug into a preamp for a magnetic phono. There was no input transformer in the preamp.

[Radioroslyn]

So where is your cartridge connected now? There is no transformer there now right? I would try across R221 and if you needed more volume terminal 2 of PB-1.

As always as John said check your voltages around the 7X7 &7AF7 you may find an out of tolerance plate resistor or a weak tube. This will insure your amp is in good order. The 7X7 triode is the preamp for the am and fm detectors only not the phono.The 7AF7 1st section is the phase inverter and 2nd section is the phono preamp. In the phono position the signal goes from the 2nd 7AF7 section to the 7X7 to the 1st 7AF7 section then to the 6V6's. 

https://philcoradio.com/library/download...6-1947.pdf

[Marsupial]

MrFixr55, wouldn't the 47-1230 expect 3v input on the phono in connector? And thus making a ceramic low by comparison?

Before I installed the vm-1200a on the 47-1230 I had it tested on other (modern) amps. Level was low on aux but somewhat appropriate on phono. That's why I ventured to make my own preamp.

I'd rather add an external preamp than alter the 47-1230 circuitry.
Perhaps I should just get a tube phono preamp...

[MrFixr55]

Hi Marsupial,

No, the 47-1230 would expect a much lower input voltage.

Crystal cartridges have an output of 1-3V, ceramic cartridges about 100-500mV, modern magnetic cartridges about 2-10 mV

Check the specs for the Phono input of the amp that you tested the turntable with.  The Phono input on most "Modern HiFi" amps are designed for a magnetic cartridge which usually has an output in the order of 10 mV (millivolts).  For example, a Fisher 400 receiver, the last tube Fisher, has an input sensitivity of 4mV for magnetic cartridges and for phono "hi", a sensitivity of 140mV.  For a Heathkit WA-P2 preamp, the Phono input was for "less than 100mV", Aux inputs for more than 100 mV with gain pots for each input.

If you can, take a photo of the cartridge in your phono.  The vast majority of V-M changers came with crystal or ceramic cartridges and were designed for "suitcase" phonos or radio-phono combos.  These were good "salt of the earth" units, certainly not something that Toscanini, Bernstein or Von Karajan would have in their listening rooms.  Most of these had rather simple 2 stage amplifiers or 3 stage push pull amps as I described.

Here is an example of a radio-phono very similar to yours, the Philco 47-1227.  The main difference is that this unit uses the Philco D10 changer with a crystal cartridge as opposed to your radio which uses the D10A with the magnetic cartridge.  The link to the documents from the Philco Library are here:
https://philcoradio.com/library/download...6-1947.pdf

Here is the manual for the D10 and D10A changers:
https://philcoradio.com/library/download...6-1947.pdf

A copy of the schematic of the Audio section is here.  Note the lack of an extra preamp stage.  The Radio and Phono input to the same stage:
   

Sorry, I currently do not have any turntable with a crystal or ceramic cartridge to run experiments with.  The last tube console I had was a Magnavox, and I replaced the Collaro turntable with ceramic cartridges with a Garrard 40B with a Pickering P-ATE3 magnetic cartridge and a Radio Shack tin box Phono amp to convert ceramic inputs to magnetic inputs.

Honestly, I think that the cartridge is going sour on you.

To be sure, take a pic of the cartridge.

[Marsupial]

Thanks a lot for the help and explanations, this is very informative. 

I am pretty sure the cartridge is the original from (I think) 1953. The vm-1200a bears the name Stromberg-Carlson if its any different. 

Here are some pictures. I am not certain what it is we're trying to look at, I can take better pictures knowing what to focus on. 

   

   

Can it be an impedance matching issue? 
I currently have the mono rca connector from the vm-1200a paired to the rca looking connector out of the 47-1230 that was meant to go in the matching transformer.
Perhaps I should connect differently?

[Marsupial]

Also, could I "easily" change the cartridge for something more efficient?

By "easily" I mean, without changing wirings or tone arm...

If I was to do that, what should I be looking at for a replacement?

[MrFixr55]

Hi Marsupial,

Sorry for the length of this, it is how my brain works. To reiterate some things here.

A clearer picture of the cartridge would be useful. If you can't lift the arm further but can move the arm horizontally, turning the turntable over and moving the arm to the outside of its movement, you may get a good shot. I am most interested is a good pic of the cartridge. I have a lot of questions. Try to answer them if you can and I can give you better recommendations.

When you hook the turntable to your Philco, you receive audio but it is not loud, only half as loud as the radio. Is the sound decent or poor? How is the sound on the radio?

The turntable has an "RCA" plug output?

You connected the turntable with the RCA plug "Pin" connected to the line to the audio stage grid and the shield to chassis ground?

When you hook up the turntable to the phono input of a modern Stereo receiver, you receive decent sound, but still at somewhat low volume?

What is the make and model of the receiver or amp that you tested the turntable on?

V-M made their own phonographs (When I was a kid, parents had a V-M 316 Stereo). However, they also made most of the record changers in almost every mid-range phonograph, radio / phono or TV / Radio / phono from the US from the mid 1950s to about 1970 when the British Garrard 40B became popular here. This is why your turntable is branded Stromberg Carlson.

Almost all of these turntables came with either a crystal or ceramic cartridge. A few came with the GE RPX magnetic cartridge. This would be the ideal replacement for your cartridge as the RPX should drive the phono section of your Philco without mod. However the tone arm for the RPX is different from the tone arm in your turntable. It has a hole at the top to change over the needle and the head is wider as the cartridge is wider than what you have. In addition, a new RPX or it's replacement is over $100.

Do you have the original record player that the turntable came from? Did you hear the phonograph before you removed the turntable?

Does your cartridge have an LP stylus on one side and a 78RPM stylus on the other side and a lever at the front of the tone arm that rotates the cartridge? If so, it is definitely not a magnetic cartridge and is likely a crystal cartridge with an output of between 1/2 and 1 volt, designed for a 2 stage tube amplifier

Do you have a modern turntable with a magnetic cartridge? If so, connect it to your Philco. If as loud (or louder) and better sounding then the V-M, then this proves that the problem is the cartridge.

How to go forward is difficult here. I am almost positive that your cartridge is dying, especially if it is a crystal cartridge. There are several alternatives dependng on how much you want to spend, whether you can try a modern turntable with a magnetic cartridge on your Philco and other considerations. This turntable can work but if a Garrard RC88 with a GE RPX dropped into your hands from above, then grab it. If it physically fits it would be the best replacement.

If you are trying to not modify the radio, then the cartridge of choice is a Shure M3 or M7 series cartridge. These are stereo cartridges with relative high tracking and may fit into the tonearm. The outputs need to be ganged. However, these are old cartridges, the needle is a little hard to get and the combination of cartridge and new needle may be expensive. In addition, the arm will sit high on the record and
may not lift sufficiently.

The following site may be helpful. Please note that this is not an official recommendation either by me or by the Philco Phorum. This is the V-M Enthusiasts website and is a business, not a non-profit like us:
https://www.thevoiceofmusic.com/default.asp

An alternative ceramic cartridge is described here:
https://thevoiceofmusic.com/catalog/part...?PID=P1943

An alternative magnetic cartridge is here, However, it is LP / 45 only, no 78 and the tracking weight is likely much lower than this arm can deliver. The price is good.
https://thevoiceofmusic.com/catalog/part...Categories=

I am not going to be back till later tonight, bbut I am very happy to help you.

[Marsupial]

I got the vm-1200a as-is without whatever it came from. One of the main factor is that it fits in the record changer tray of the 47-1230 - it is currently secured in there.

The cartridge uses a double stylus and there's a twist knob to switch between the two... But I don't have any 78 rpm records to play on it.

When I was preparing the vm-1200a to be assembled in the radio, I ran tests by connecting it to a 1970s era radio/amp unit for which I can't say the model at the moment (it is in my shed that's currently snowed in, happy winter) and the volume was not overwhelmingly low, the sound very clear. It wasn't as low as what I get on the Philco.

Here is a photo of the stylus, and the cartridge with and without the stylus. 

   
   
   

I'm OK to alter the radio, but only in a manner that would make sense for the next guy who will do maintenance in there.

[MrFixr55]

Hi Marsupial,

Sorry for the delay, I got busy with several other issues but also did a bit of research that is hopefully helpful.

The needle for your turntable is available from the V-M Enthusiasts website given in the previous post.  Your turntable uses a Shure Ceramic cartridge having an output of somewhere between 250 mV and 700 mV, but I don't know which model your turntable uses.  There are currently 2 Shure cartridges of this vintage on eBay.  There is no info on these cartridges on either the Voice of Music Enthusiasts website or on the Shure website. 

The VM website has several cartridges that may fit your tonearm, some as cheap as $20.00 plus shipping.  Some info from that website is in the doc below that I put together from their website:

Philco 47-1230 VM turntable conversion.pdf Size: 265.18 KB  Downloads: 133

V-M Phanstihl Astatic P51 Cart.pdf Size: 38.62 KB  Downloads: 111

Below is the service document for the Philco D10 and D10A turntables.  Read these as it may give you further insight to this issue.
https://philcoradio.com/library/download...6-1947.pdf

Reviewing the D10 and D10A turntable service manuals from the Philco library, the D10 (not your old one) uses a crystal cartridge, likely having 0.5V - 1V output.  The D10 A that you removed from the set used a magnetic cartridge.  The instructions state that the extra audio stage in the D10A has a gain of about 5.  There are instructions in the D10 manual that may be helpful.  I base the following inswtructions on the procedure in the manual.
You can test the phono amp in your Philco by doing the following:
Tune the radio to a quiet spot on the AM Band.  Set the volume control at ab out 1/4 of the way.
Using a CD player with a headphone output and a blocking capacitor, connect the output of the CD player to the "FM Test" point on the radio, set the Radio-Phono switch to Radio and set the volume on the CD player so that it is barely audible.  Now connect the CD player to the phono input and set the Radio - Phono switch to Phono.  The volume should increase significantly, likely to a comfortable or loud listening level.

Do you still have the original D-10 A turntable?  if so, connect it watts and all and do a "scratch the needle test.  If the scratch is loud and proud, then the audio amp circuit works.
I used the term "modern" magnetic cartridge in previous posts.  The original Victor "Electrola" turntable from the late 1920s to early 1930s used a magnetic "head" that produced a "radio level" output (likely between 500mV and 1 volt) that would drive the audio amp of a standard radio of the times.  However, the  Electrola also used a step-up transformer, and the head was massive and had the same tracking weight as the original acoustic sound box which was somewhere around 20-30 grams.

[Marsupial]

Thanks MrFixr55. There's no rush, we all have lives... Thanks a lot for helping out. 

I no longer have the d10a - its motor was seized and didn't have styluses, I gave it to another phorum member years ago. I didn't feel like investing that amount of time and money to bring back a 78rpm changer when all I have is 33 and 45 - I'm not sure if it ended working again.

My current stylus I have is from the v-m website. For a commercial site, they were very generous of their time and were useful identifying and helping me bringing the turntable back to working order.

How do we select replacements when we change cartridges?
From what you said, I feel like the best course of action would be to go to a magnetic cartridge?
Can we connect a stereo head to a mono tonearn?

If changing the cartridge has the option of solving the problem, I'm thinking about going forward with it-but I'd like to be sure of ordering the good parts. 

Thanks!

[MrFixr55]

Hi Mars,

Yes, you could put a stereo magnetic cartridge in that turntable, but I don't know how successful it would be. 

Here are the variables:

• Finding a cartridge with 1/2" mounting holes- Easy.
  
• Having to put the 2 sets of terminals on the cartridge in parallel- Relatively easy, requires the slip-on connectors, cannot solder directly to the pins of the cartridge.
  
• Cartridge height (how far it hangs below the arm)- Moderate difficulty, if cartridge hangs too low, needle will drag across record or turntable when changer picks up arm.  there may be a few choices on the V-M website.
  
• Tracking- Moderate difficulty.  Need to find a magnetic cartridge that tracks between 5 and 10 grams.  this turntable will not track at a low weight such as 1-3 gm.
  
• Confirming that the Phono Amp has 10mV input sensitivity- Difficult, see below.
  

Unless one of the Phorum Old timers (oh well, we all are kinda on the old side) was able to find specs for the magnetic cartridge that was part of the D10 turntable, the sensitivity of the "phono amp" that is part of the radio is a guestimate.  None of the documents for the radio or turntable give sensitivity for either the Phono amp or the regular input from the radio.  I estimate that the crystal cartridges of the time used on the D10 (not the D10A), and in the 47-1227 (see previous diagrams in this thread), put out between 0.5V and 1V.  My rough guess is that the Phono preamp on this set has a sensitivity of about 0.1V OR 100 mV.  The best way of determining if a magnetic cartridge is appropriate is to actually hook up a turntable with a magnetic cartridge to the "phono" input to the radio.

Can you borrow a turntable with a magnetic cartridge for testing purposes?  Testing the Phono Amp is the first stage of decision making.

When you can dig out the HiFi Amp that you tested the turntable with, please post the make and model.  The manual may be available that gives the input specs for the amp.  I suspect that the input sensitivity of the Mag Phono input on your HiFi is in the 10mV range.  Since Ceramic cartridges are somewhere between 300 and 500mV or a little higher, your having to use the mag phono input of your HiFi amp is the reason that I think that your cartridge is dying.  If it was a crystal cartridge, it would be dead.  I don't think that any crystal cartridge this old would be good.  

Gotta get ready for church. If not enough gain, add 1 triode stage of amplification using a 6F5 or 6SQ7 (if you are trying to be period correct)  Alternate is to do a little hidden under chassis mod to switch in or out the Phono amp, and have a pigtail with a female RCA connector on the 1st AF amp to either add a little solid state mag amp or use a ceramic cartridge.

[Marsupial]

How unsuccessful can installing stereo become? Should I look for mono cartridges?

It seems I should aim at ceramic cartridges from v-m that would physically fit my tone arm and record changer mechanism. And if that doesn't do it, add amplification.

If the cartridge isn't dying, should I assume it is going to happen sooner than later anyway?