HMV or Marconi table top radiogram ID needed.

[vinrads]

Just got round to looking at this again ,no radio . I thought it was working ok when last tried , after restoration, it is in need of an pick up arm and pick/up ,It looks like I did the multi capacitor block some time ago poss 15/20 years , any pictures of the arm would be appreciated .Mick.

[Cobaltblue]

HMV 501 if you do an on line search for pictures you will see the arm which was a pretty common type on HMV/Marconi single players around 1932

Cheers

Mike T

[vinrads]

Thanks for that Mike , It looks like it has been fitted with a 110 volt tx for the motor can anyone confirm the motor needs 110volts , Mick.

[Cobaltblue]

I have a 501 but its been in deep storage for 25 years.

I did quite a lot of work on it back then and I don't recall the motor being 110V

There is some contemporary service information here

https://www.service-data.com/product...57/3615/s12757

Cheers

Mike T

[Techman]

Trader sheet 563 also available for it from 'up top', too -

https://www.service-data.com/product...48/4379/t13548

[vinrads]

Having downloaded the cct , there are several differences ,the one I have has an HT choke not a 2k resistor , also the cct shows six resistors on a tag board mine has fore .
The motor fitted has the numbers 225 and 25c stamped on it ,also there is a tx shown on the chassis marked tx3 ,is this the original mains tx I am thinking mine has had a replacement mains tx external to the chassis . ! I am just about to connect the motor to the 110v tx . Mick.

[PaulR]

There must have been several versions. Here are some photos of one I did a long time ago. It has 7 caps in that box

By the way, did you re-polish the case?

[vinrads]

Thanks Paul , I think you are correct there must be several versions , my capacitor block has three rows of contacts, I had this hum low level but annoying ,I found that a 41MH detector reduced it ,and also sounded better it had a mhl4 fitted , I will be looking for a new 41MH as this one is a bit noisy at first .
Regarding the cabinet I stripped it but had it professionally finished some years ago . Mick.

[PaulR]

I could never get rid of an annoying hum on the one I did which was for a friend. Looking at the photos this was in 2007. I must get it back to have another look at it.

I seem to remember that it had an odd "3D" chassis that wasn't the easiest to work on

[Techman]

Originally Posted by PaulR

There must have been several versions.

I guess that seeing as the set was released in 1931, but the circuit wasn't published until 1942, I'm thinking that there may well have been a few manufacturer modifications and upgrades in that decade.

It states that it's able to be set to run on mains voltages from as low as 95 volts to as high as 260 volts, so I would guess that it probably has a motor wound for 95 (ish) volts (110 volts closest common value) and it uses the primary of the mains transformer as an auto-transformer, which sets the overall voltage for the radiogram. Is it one of those eddy current induction type motors with a disc similar to an old style electricity meter? Although I think most of those were wound for standard mains voltage, but there were probably exceptions - I've not had dealings with one of that type for very many years.

[vinrads]

Thanks for that , this one has a brush motor ,two field coils in series with the commutator ,it seems to run ok with 110 volts all the fixing holes ok and the speed control is in the right place ,just to add the 110 volt tx is an addition along with a mains tx , Mick.

[Cobaltblue]

When I did mine I used the information in Newnes Complete Wireless which was 1932 so contemporary with the set.

My set was a pretty close match to that information which I linked to in post#4 if you have Pauls DVD 1 it is actually on the disc as 501 AC other.

Hope that helps.

Cheers

Mike T

[Techman]

I've come across brush motors in old Garrard decks before. This is so that they can also run on DC mains. It seems that when the primary of the transformer is used as an 'auto' for the motor, that although this seems like a good idea in theory, in practice it seems to result in a burnt out primary - had this before myself on a gram I repaired for someone years ago.

So it's no surprise that it's got two replacement transformers now fitted. It could be as said above, that the motor was across the lowest tapping on the transformer primary and it eventually burnt out, or it could also be that the set was originally the DC mains version which would have had a great big rheostat in series with the gram motor (seen this before myself) and someone decided to convert it to AC only using a couple of separate transformers. I suspect that this latter idea is less likely than the first one, in that the original transformer just burnt out and it was better and easier at the time to just fit two separate replacement transformers.

The above is all just supposition, as I'm not familiar with the particular model radiogram being described in this thread, but from other old similar kit that I've looked at in the past.

[vinrads]

Hi Just found an old thread , the rectifier and two transformers were mounted on a piece of plywood ,looks like I had a memory failure in that department , the hole for the rect had never been used on the chassis, but it is now ,so that makes it a DC version originally , still looking for a tone arm and platter ,I would love to get this up and working again done the radio/amp bit , Mick.

[vinrads]

Update on the motor, having run the motor on 115v ac all seemed to be ok then all of a sudden it started to run slow hardly any torque ,tried it with 115 dc ,the windings get hot ,then connected the variac to the bridge rect ,found the motor runs nicely better speed stability and will start rotating with the needle on the record with about 30 volts at 200ma ac in .Mick.