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Old 20th Sep 2018, 1:40 pm   #1
brightsparkey
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Default SABA Dorchester - repair

I have acquired a radiogram, having sworn not to, but was swayed by low price and it kept looking at me in that lost way etc..

Its a SABA Dorchester from 1965 - it has a stereo radio and a Dual 1011 Record deck. Fitted with a 13A 3pin plug, but the seller had not plugged it in,thankfully.

Internally its interesting - 4 speakers in each end of the cabinet - large elliptical bass, closed shell mid and two tweeters. Sophisticated cross-overs with chokes and non-polar electrolytics. As well as the deck and radio chassis there is a drawer for a reel-reel tape deck with slides, a light with switch for the record deck to illuminate the cavity when the lid is opened and finally a mes lamp with a light pipe that goes through a brass ferrule to the front panel to show 'power on' when the radio is covered over..

I removed the chassis, which is the same as a Freudenstadt 15, and got to work on the set. PAT test showed no issue with insulation and the transformer had continuity. Amazingly the electrolytics were all OK, holding charge, so I gently powered the set up on some dummy speakers and a variac and lo- there was sound on FM ! Amazed.

But not all was well, and it can be deceiving when the set appears to work, but actually it had quite a few faults still.
  • One side was no audio - 220k resistor on the anode of the ECC83 audio triode was O/C
    Other side audio triode had that resistor already replaced with a 1W 22k resistor (!) which was replaced with correct value.
    Checked all other resistors with >50V - all had been either already replaced or were O/C
    • Both Magic eye anodes R318 and R333 - both O/C
      FM 1st IF stage supply R16 - already replaced
      Both ecll800 phase splitter triodes anodes R432,532- both O/C - amazing that good quality audio was still present with these open!! Brute force of feedback I guess
      Dropper R608 was OK, but a little high. Replaced anyway.
    Selenium bridge had been replaced with a single silicon diode - replaced with Selenium rectifier bridge kindly provided by list member.. works well.
    EMM803 magic eye was almost black in the phosphor and exceedingly dim - replaced with a part worn tube also kindly provided by a list member.

Cathode voltages on the output stage are bang on, and the whole set now draws the right current. All the capacitors are OK, mostly Wima film capacitors (originals, but the set is 1965 so no more wax caps). Even the electrolytics are universally OK, even in the crossover.

Mechanically the set works OK - all strings present, but the thimble on the tuning rod jumps and clicks - I suspect it maybe wound incorrectly.

The whole set is covered in a brown coating. Its not kitchen grease and there is no smell of tobacco - I'm at a loss to know what it is. It will scrub away with IPA (not of the beer variety). The white paint on the dial back is completely obliterated. Gentle scrubbing with a brush and IPA removed the stuff but also left the paint below it a bit thin with much coming off.

Antenna switch needed a good wipe. Pots were OK. I removed the scale glass to clean the back plate and discovered the reason why the left clip was sticking up at the end - a screw had got in the fabric in the clip- probably in the factory Scale is actually glass and in good shape - just needed a good clean on the front face only. I cut a paper sheet to cover the back plate as a reversible fix for the brown coating and now the scale is legible again.

Amazingly the scale lamps both work. Discovered that my stock of scale lamps have the wrong screw thread which is why the don't seem to fit on anything

Once the dead resistors were replaced, the radio is working well with excellent FM performance and good on AM too. Nice deep sound in the case with the full set of speakers. Just need to find a permanent home for it now.. its a bit Teak 1970's looking for our decor.

Left to do:
Replace mains Lead and earth the chassis - hope this does not compromise hum on phono stetting.
The set has no stereo decoder but I have sourced one which is on its way.
Fix up the case-work which has a few deep scratches and a chipped corner.

The record deck is due for a different thread, but it had a waxie cap in it - only one in the set and , of course it had failed short

Kevin.
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Last edited by brightsparkey; 20th Sep 2018 at 1:46 pm.
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Old 20th Sep 2018, 2:38 pm   #2
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Default Re: SABA Dorchester - repair

Quote:
Originally Posted by brightsparkey View Post

it has a stereo radio

The set has no stereo decoder

Kevin.
That seems to be a bit of a contradiction?

No need to replace the mains lead unless it's actually defective in some way, leave the original two core only, as no exposed metal parts. If you fit a three core lead and earth the chassis, then it legally has to comply with the latest regulations, which it can never do, and you'll become responsible for a non-compliant modification.

Having said all the above, I do sometimes fit a three core lead as a replacement for a two core if I buy a set that has come from the auction house where they sometimes cut off the original mains lead. If I happen to have a three core lead with a 13 amp plug attached to hand, that I've cut off something else, then I use it, but normally I leave as original and stay legal.

Nice radiogram, though

Edit: Just a thought with you appearing to find all those o/c resistors - I'm wondering whether your DVM doesn't have a high enough ohms range to actually measure them and they've actually just gone very high in value, thus the fact that the set was still working to some extent, just a thought.

Last edited by Techman; 20th Sep 2018 at 2:46 pm.
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Old 20th Sep 2018, 2:55 pm   #3
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Default Re: SABA Dorchester - repair

Yes, very nice, a top flight stereogram in its day. I would be very surprised if there was a factory fit stereo decoder in a 1965 stereogram but it could be one of the very first ones. I'm not sure when the Germans started stereo broadcasting. Some American stations were stereo in 1965 so it could have been primarily intended for that market.

The brown coating is very likely to be tobacco tar, which doesn't always smell of stale fags. An uncle and aunt of mine were heavy smokers and there was a thick brown coating over everything - walls, furniture, TV etc. I acquired a few of their things after they died and it was a fair old job to get it all off, though foaming cleaner dissolves it quite well.
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Old 20th Sep 2018, 3:43 pm   #4
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Default Re: SABA Dorchester - repair

I suppose you could say the set was 'stereo ready' For phono it is stereo and there are two independent push pull amplifiers. The radio has a socket for the decoder and the stereo indicator on the front panel. I guess the decoder was an option. The original SABA bypass plug is in place.

The set seems to be targeted at the UK specifically, as the same set is also called 2560US for the American market with altered de-emphasis. There is also an 'Excelsior' variant (not sure for where).

Tobacco tar - maybe the smell goes after a while ? - would make sense. Makes for a-lot of trouble. I hate to use solvents as you never know what will wipe away along with the dirt..

W.R.T. mains adaptation (hoping not to ignite a flame war..) - in what regard would a modification not be 'legal'? Three core flex, with earthed chassis, fused and switched, and tested to ensure adequate insulation strength, all exposed metal parts bonded to earth with adequate weight conductors. What am I missing? Much harder to achieve 'double insulated', I would have thought..

The resistors are O/C as in >10Mohm, the limit of the lab's fluke 75 handheld meter, instead of 10's or 100'skOhms, so I guess they could still admit a small dribble. I suspect they are carbon film composition and the electric field has stripped them by migration of the carbon. This is a common effect in a certain types of construction. Its only the 1/4 watt ones that failed and they're all the same type.

Kevin.
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Old 20th Sep 2018, 8:07 pm   #5
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Default Re: SABA Dorchester - repair

I think the first stereo transmissions in Germany were in 1962, a few years ahead of our part of UK back then.
My 1963 NordMende Tannhauser had a stereo socket with dummy plug, to which I retrofitted a 1965 ish stereo decoder. I bought a slightly NOS "Bornholm" in 1967, 1965 manufacture I think. No decoder fitted but I bought one and just "plugged it in". Later I had a stereo portable "Phonosuper" fitted with decoder from new, as was the 1967 Parsifal which sits upstairs today, whilst I wonder do I sell it or put it in the living room (could cause a fight of course).
As an aside, the decoder i fitted to my Bornholm included an SCA trap (Store cast) so was obviously also suitable for the US market, where a lot of their models were specifically aimed.
Les.
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Old 20th Sep 2018, 8:13 pm   #6
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Default Re: SABA Dorchester - repair

Kevin's thread on the Saba forum: http://saba-forum.dl2jas.com/index.p...coder-options/
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Old 20th Sep 2018, 10:23 pm   #7
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Default Re: SABA Dorchester - repair

Thanks for putting up the link. It's a useful forum for Saba radios, and Google translate makes it much more accessible these days.

It's fascinating to watch the improvements made in successive decoders, and compare with the Grundig I have too. I discovered that the explanation I got at college of how FM stereo works was accurate but misleading - once you see how it's decoded the scheme makes perfect sense.

Kevin.
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Old 20th Sep 2018, 11:59 pm   #8
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Default Re: SABA Dorchester - repair

To put iceing on the cake, may I suggest adding accoustic wadding to the speaker boxes. Any resonances in the enclosure will be dampened.
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Old 21st Sep 2018, 7:37 am   #9
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Default Re: SABA Dorchester - repair

The rotatable ferrite aerial is a great idea as it saves you from having to position the radiogram at an angle to the wall!

But what is the purpose of the relay running along the pulley directly beneath it?
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Old 21st Sep 2018, 7:52 am   #10
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Default Re: SABA Dorchester - repair

That is quite a bit of kit!
Most impressive speaker array too, wonder why they fitted two tweeters per side?
Anyway, as regards the brown film over everything it is most likely the exhaust from cigarettes etc. as others have observed. It can be the devil itself to get off but I have found a foaming cleaner which seems to eat it alive, we use it for degreasing where I work, its called Ambersil Anti-Static foaming cleaner. I have no connection with Ambersil just that it works extremely well, also gets the crud out of the grooves of Bakelite knobs if left to soak for a few minutes.
Excellent project, keep up the good work!
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Old 21st Sep 2018, 2:18 pm   #11
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Default Re: SABA Dorchester - repair

Ken, I assume you are referring to the contacts by the ferrite rod? This is a standard SABA arrangement. The contacts switch out the ferrite antenna and connect the external antenna socket for AM, the knob points to 'Aus' or 'off' when the contacts are connected.

My other SABA from the 1950's has this too - in that case there is a little window with numbers and 'aus'. Such features are the DNA of the manufacturer

Kevin.
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Old 21st Sep 2018, 2:20 pm   #12
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Default Re: SABA Dorchester - repair

It may not be apparent from the photo, but the two tweeters are set at an angle to the left and right, so I guess they are trying to achieve a wide dispersion pattern. A bit like the 3d-sound concept on table top radios.

Thanks for the hint with the cleaner and as previously mentioned by Paul. I think we may have the very same product in our lab already. Will give it a whirl.

Kevin.
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Old 21st Sep 2018, 2:59 pm   #13
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Default Re: SABA Dorchester - repair

Regarding wadding in the speaker housings - I plan to do some proper testing when I get the opportunity - this requires open space (the garden) and some test equipment and mics. Garden is full of diggers at the moment in preparation for the new workshop ..

Will report in once I've done some investigations.

Kevin.
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Old 21st Sep 2018, 2:59 pm   #14
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Default Re: SABA Dorchester - repair

To answer your question about mains adaptation, it comes down to whether the changes can be considered repairs or modifications. It the latter, then the type approval rules that applied at the time of manufacture no longer apply and everything has to comply with the current regs. Obviously this is a legal minefield so most people avoid doing anything that could be considered a modification, even if that would make the appliance safer.

A certain amount of common sense is called for of course, and most people do indeed earth a radio chassis when doing a restoration (unless it's an AC/DC set).
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Old 21st Sep 2018, 7:55 pm   #15
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Default Re: SABA Dorchester - repair

Quote:
Originally Posted by brightsparkey View Post
W.R.T. mains adaptation (hoping not to ignite a flame war..) - in what regard would a modification not be 'legal'? Three core flex, with earthed chassis, fused and switched, and tested to ensure adequate insulation strength, all exposed metal parts bonded to earth with adequate weight conductors. What am I missing? Much harder to achieve 'double insulated', I would have thought.
Hi Kevin, glad the EMM803 has found a good home.

Actually 'Techman' is absolutely correct in his statement about the three core mainslead. It may sound stupid but IN THE EYES OF THE LAW (and the Safety Standards committee) the radio was designed with a two-core lead and met and complied with the standards OF THE TIME. As long as the set is used in its original form it still meets the standards OF THE TIME. However if you fit a three-core lead, that is changing the original design and no longer complies with the standard to which it was tested (since it wasn't required to have an earth). Technically it should be re-tested for Class I and it probably wouldn't pass the leakage requirements.

Of course I'm going 'by the book' here and I'm not trained in legal procedures...I only safety-test products to the current version of the standard. You and I know that if you earth the chassis it won't do any harm (other than perhaps to strain the insulation of the mains transformer since the primary will now have a reference to earth via the bobbin former...which is probably impregnated cardboard rather than plastic) and of course if it breaks down it will blow a fuse anyway. For your own use....fine. However if the radiogram is passed on to someone else and something happens, you could be held responsible for carrying out an unofficial mod.....!

Anyway let's not get involved with anything to do with legal right and wrongs here.

It looks to be a great item and should sound good.
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Old 21st Sep 2018, 7:59 pm   #16
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Default Re: SABA Dorchester - repair

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A certain amount of common sense is called for of course, and most people do indeed earth a radio chassis when doing a restoration (unless it's an AC/DC set).
Absolutely! Unfortunately 'common sense' and 'safety standards' don't always go together......
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Old 27th Sep 2018, 9:21 am   #17
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Default Re: SABA Dorchester - repair

A minor error in the schematic where a voltage measure is connected to the wrong wire. The signal labelled 'X' is close to ground, from the FM discriminator - the label is meant for the anode of the EBF89 instead..

I noticed this while working out the connections for a newly arrived stereo decoder.
Kevin.
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Old 27th Sep 2018, 6:31 pm   #18
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Default Re: SABA Dorchester - repair

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Sadly it does not seem possible to join the forum as registration requires the use of “Captcha V1” which no longer works.....
Shame, I’d like to join but my German is not upto writing directing to the owner.

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Old 28th Sep 2018, 9:53 pm   #19
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Default Re: SABA Dorchester - repair

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I’d like to join but my German is not upto writing directing to the owner.
Hello Peter,
write in English, in former Western-Germany you learn English in school, so it will no problem.
I had the same problem here, never sure if I write English or German with English words.

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