Stella ST234A - Any Info? - UK Vintage Radio Repair and Restoration Discussion Forum

wardster · 4th Aug 2008, 12:17 am

Hi all - Just found this website as I'm looking at restoring a couple of nice old valve sets bought recently.

The first is an ST234A, S/N M7900, with the original valve location sticker with a pair of EF80's, ECH81, EF85, EABC80, EL84 and EZ80.

All appears well apart from the bulbs, as switch on with a limiter bulb gives reasonable reception on all bands, but VHF top end (100 MHz) seems quiet?

I'm looking at attempting to detune the set so that the range is moved from 88 - 100 to more like 92 to 104, so, does anyone have any info in regards to a circuit diagram as all sources seem to have failed with this one!

Also.... the tuning cord has snapped. The set seems to be particuarly complex as the VarCap is mounted vertically on the left hand side of the chassis in what looks like a bolt on module!

Anyone with any help would be appreciated

Pete_kaye · 5th Aug 2008, 3:12 pm

I recently fixed a Stella 239U(see earlier posts) and found it simple to shift the VHF band up to include Classic FM on 101 MCS by resetting a trimmer in front of the tuning coils / slugs mechanism ..without losing the bottom end so still have 88.5Mcs.Reception will be affected when running through a bulb limiter .Try the highest wattage (100W) you have then take the plunge.
I used kite twine for rewinding the tuning cord and after 3 weeks it is still fine.
have you tried the library for circuits (eg Sheffield central)?

paulsherwin · 5th Aug 2008, 4:32 pm

You can buy a scan of the Radio & TV Servicing pages for this set from Paul Stenning for £1.99 by clicking on the link at the top right of the screen. The charges help fund this forum.

Some libraries keep copies of R&TVS in the reference section or in the reserve stacks. It's worth asking the staff.

You will find the FM reception will be significantly better without the lamp limiter.

Paul

wardster · 5th Aug 2008, 4:52 pm

Thanks for replies. Due to my job, getting to the main library in Sheffield is difficult! But, I cannot find the Service / Trader sheet for this model of radio in the VRSD!

http://www.digitalengines.co.uk/stella.jpg

Heres a pic to help ID!

Also, on the back, it is marked MK40012. Is this another reference number?

Sideband · 5th Aug 2008, 9:25 pm

You will find that this is the Stella version of the Philips 353A. This should be available from the VRSD.

My 353A works well up to 102Mhz without any tweaking. However EF80's struggle at VHF above about 100Mhz so you may not be able to stretch much above what you already have. I would be surprised if you can get 104Mhz. You do need good valves in these positions. If you do a forum search on Philips 353A, you should be able to find my restoration account of one of these.

Good luck.

Rich.

paulsherwin · 5th Aug 2008, 9:35 pm

You're right, Paul doesn't have the ST234A listed - I was sure he did. He does have the Philips 353A: http://www.service-data.com/section.php/5793/1. Philips reused essentially the same chassis in a range of Philips, Stella, Cossor and Mullard radios in the mid 50s.

If you only buy one of the documents, the manufacturers' data would be the best choice.

You may find the VHF high frequency performance is better if you replace the EF80 valves with the later EF184.

Good luck, Paul

johnn · 9th Aug 2008, 12:19 pm

I have done a trial on my 353A with EF184's & they improve things receiving Classic FM. I have not tried above 101.5MHz. Changing the mixer/oscillator EF80 moves the tuning range on this set, but is this normal?

John

Steve_P · 9th Aug 2008, 12:41 pm

Possibly. The set was designed with the EF80 in mind, and putting another valve in will change the characteristics of the circuit. Sometimes in a small way like this.... sometimes with a loud bang!

In this case though, one of the EF80s will be an RF amp, the next one will be a mixer. This is the one that caused the change. I am sure that there is no harm in it, but you may have to tweak the VHF front end slightly to return the set to it's original state. If you need to that is.

Cheers,

Steve P.

johnn · 12th Aug 2008, 7:45 pm

Thanks Steve. I have not changed the front end tuning,
John.

4th Aug 2008, 12:17 am	#1
wardster Retired Dormant Member Join Date: Aug 2008 Location: Chesterfield Posts: 3	Stella ST234A - Any Info? Hi all - Just found this website as I'm looking at restoring a couple of nice old valve sets bought recently. The first is an ST234A, S/N M7900, with the original valve location sticker with a pair of EF80's, ECH81, EF85, EABC80, EL84 and EZ80. All appears well apart from the bulbs, as switch on with a limiter bulb gives reasonable reception on all bands, but VHF top end (100 MHz) seems quiet? I'm looking at attempting to detune the set so that the range is moved from 88 - 100 to more like 92 to 104, so, does anyone have any info in regards to a circuit diagram as all sources seem to have failed with this one! Also.... the tuning cord has snapped. The set seems to be particuarly complex as the VarCap is mounted vertically on the left hand side of the chassis in what looks like a bolt on module! Anyone with any help would be appreciated Last edited by paulsherwin; 4th Aug 2008 at 12:23 am. Reason: Edited to comply with forum rules

5th Aug 2008, 3:12 pm	#2
Pete_kaye Octode Join Date: Jun 2005 Location: Sheffield, South Yorkshire, UK. Posts: 1,227	Re: Stella ST234A - Any Info? I recently fixed a Stella 239U(see earlier posts) and found it simple to shift the VHF band up to include Classic FM on 101 MCS by resetting a trimmer in front of the tuning coils / slugs mechanism ..without losing the bottom end so still have 88.5Mcs.Reception will be affected when running through a bulb limiter .Try the highest wattage (100W) you have then take the plunge. I used kite twine for rewinding the tuning cord and after 3 weeks it is still fine. have you tried the library for circuits (eg Sheffield central)?

5th Aug 2008, 4:32 pm	#3
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,966	Re: Stella ST234A - Any Info? You can buy a scan of the Radio & TV Servicing pages for this set from Paul Stenning for £1.99 by clicking on the link at the top right of the screen. The charges help fund this forum. Some libraries keep copies of R&TVS in the reference section or in the reserve stacks. It's worth asking the staff. You will find the FM reception will be significantly better without the lamp limiter. Paul

5th Aug 2008, 4:52 pm	#4
wardster Retired Dormant Member Join Date: Aug 2008 Location: Chesterfield Posts: 3	Re: Stella ST234A - Any Info? Thanks for replies. Due to my job, getting to the main library in Sheffield is difficult! But, I cannot find the Service / Trader sheet for this model of radio in the VRSD! http://www.digitalengines.co.uk/stella.jpg Heres a pic to help ID! Also, on the back, it is marked MK40012. Is this another reference number?

5th Aug 2008, 9:25 pm	#5
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,578	Re: Stella ST234A - Any Info? You will find that this is the Stella version of the Philips 353A. This should be available from the VRSD. My 353A works well up to 102Mhz without any tweaking. However EF80's struggle at VHF above about 100Mhz so you may not be able to stretch much above what you already have. I would be surprised if you can get 104Mhz. You do need good valves in these positions. If you do a forum search on Philips 353A, you should be able to find my restoration account of one of these. Good luck. Rich. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

5th Aug 2008, 9:35 pm	#6
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,966	Re: Stella ST234A - Any Info? You're right, Paul doesn't have the ST234A listed - I was sure he did. He does have the Philips 353A: http://www.service-data.com/section.php/5793/1. Philips reused essentially the same chassis in a range of Philips, Stella, Cossor and Mullard radios in the mid 50s. If you only buy one of the documents, the manufacturers' data would be the best choice. You may find the VHF high frequency performance is better if you replace the EF80 valves with the later EF184. Good luck, Paul

9th Aug 2008, 12:19 pm	#7
johnn Retired Dormant Member Join Date: Jun 2003 Location: Scunthorpe, UK Posts: 154	Re: Stella ST234A - Any Info? I have done a trial on my 353A with EF184's & they improve things receiving Classic FM. I have not tried above 101.5MHz. Changing the mixer/oscillator EF80 moves the tuning range on this set, but is this normal? John

9th Aug 2008, 12:41 pm	#8
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Stella ST234A - Any Info? Possibly. The set was designed with the EF80 in mind, and putting another valve in will change the characteristics of the circuit. Sometimes in a small way like this.... sometimes with a loud bang! In this case though, one of the EF80s will be an RF amp, the next one will be a mixer. This is the one that caused the change. I am sure that there is no harm in it, but you may have to tweak the VHF front end slightly to return the set to it's original state. If you need to that is. Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

12th Aug 2008, 7:45 pm	#9
johnn Retired Dormant Member Join Date: Jun 2003 Location: Scunthorpe, UK Posts: 154	Re: Stella ST234A - Any Info? Thanks Steve. I have not changed the front end tuning, John.