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Radio Rentals 218.

PostPosted: Sat Aug 20, 2016 4:50 pm
by Doz
Just been looking at this for a friend. Nice set.

Re-capped all the usual 'orrible hunts, and changed the cathode bypass caps out, and it works really well on AM. Good quality from it's EL84 and large goodmans speaker... but FM isn't so good. Bass is overloaded and distorted. I take it it can't handle "modern" compression (or maybe deviation) ?

In the absence of any service info, I've marked and gently tweaked the alignment, to no real improvement. Any pointers, or is it something I'm going to have to live with?

Re: Radio Rentals 218.

PostPosted: Sat Aug 20, 2016 6:26 pm
by Cathovisor
Doz wrote:Bass is overloaded and distorted. I take it it can't handle "modern" compression (or maybe deviation) ?

Deviation is still the same as it ever was (what's done in the name of compression though...). Have you changed the stabilising electrolytic on the ratio detector? Small value but surprisingly high voltage.

Radio Rentals 218.

PostPosted: Sat Aug 20, 2016 8:46 pm
by nuvistor
The AM suppression cap is a favourite has Cathovisor says, worthwhile changing. While you are working around the ratio detector check the resistors, looks like 2x100k and 1x22k, the diodes in the EABC80 need to be a reasonable matched as well.
I cannot see one on this forum but there is a Baird 218AC manual on the UKVRRR site, if its the same it includes alignment instructions.

Frank

Re: Radio Rentals 218.

PostPosted: Sun Aug 21, 2016 5:02 pm
by Doz
nuvistor wrote:The AM suppression cap is a favourite has Cathovisor says, worthwhile changing. While you are working around the ratio detector check the resistors, looks like 2x100k and 1x22k, the diodes in the EABC80 need to be a reasonable matched as well.
I cannot see one on this forum but there is a Baird 218AC manual on the UKVRRR site, if its the same it includes alignment instructions.

Frank


Thanks Frank. The electrolytic was in poor shape, and got binned straight away. Do you have a link for the service sheet? I've done a search and can't seem to find it... The 218AC has the posh wooden cabinet, as opposed to the bakelite one. I think electrically they're the same.

Re: Radio Rentals 218.

PostPosted: Sun Aug 21, 2016 7:46 pm
by nuvistor
Link for the manual, is it worth asking Chris if he has the manual before getting the one on the UKVRRR site?

http://www.service-data.com/product.php/359/655/m10359

Frank

Re: Radio Rentals 218.

PostPosted: Mon Aug 22, 2016 6:35 am
by crackle
You can get it from the Radio Museum for free. http://www.radiomuseum.org/r/baird_m218ac.html

Mike

Re: Radio Rentals 218.

PostPosted: Sat Aug 27, 2016 7:09 pm
by Doz
Hadn't gleaned that two of the VHF alignment coils/ transformers have slugs in both ends (I feel like a right pillock). Aligned up a treat. Although modern compression on pop music still distorts, Radio 4 and 3 are just fine.

Re: Radio Rentals 218.

PostPosted: Sat Sep 03, 2016 11:40 am
by Focus Diode
The poor thing is probably protesting at the dreadful music played by most stations! Anyway a great restoration job.

Early VHF sets are nothing to write home about but was surprised by the performance given in the HMV 1131 I used to have (now have the Marconi version). LBC from Croydon could be received in Chippenham quite well using an indoor wire aerial where a modern tuner connected to a 6-element outdoor BII aerial couldn't. Aerial was in the wrong direction to be fair.

Brian