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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE! |
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28th Feb 2008, 10:55 pm | #1 |
Dekatron
Join Date: Sep 2003
Location: Bolton, Greater Manchester, UK.
Posts: 6,644
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(Let’s have some music) MAESTRO 756
Well most of you know I like the Eastern European Sets - and I thought this was one when I bought it on Ebay. But when it came, I had a bit of a shock. This set - Maestro 756 - was Turkish! Interesting to note that the BBC stations were not on the dial.
Well, the cabinet was all wood, and quite nicely made. Inside, however, it was a tidy looking rat’s nest. Metal Rectifier, then the valves were ECC85, ECH81, EF89, EABC80 and EL95. The output stage was small. It looked OK inside and out, so after changing the Control Grid capacitor, I switched on to see what it would do. This set was set up for the highest voltage it could be - 220v and here in Sunny Bolton, it’s usually 239 Volts. Oh well, it’s been used on that already, so let’s see what happens. Long Wave and Medium Wave were quite lively, Short Wave was Dead and FM was equally uninspiring. Put the set on the outdoor antenna and it livened up a lot on all three AM Bands, still nothing on FM. 10.7 Mhz got through, but nothing else. A new ECC85 brought FM in, everything was about in the right place, but FM sounded weak still. The caps on the Discriminator were changed - no joy. In fact, the whole set seemed a bit poor. A spare EABC80 improved things a lot. Two valves changed. I dropped the mains to 220v and it stayed the same, so we were almost home. A dial lamp was fitted, and a look at the valves showed that this set’s problems were down to 2 problems. Odd Manufacturer of Valves which had all been overrun. So, I needed to modify the set for 240v operation. Mains back up and measure across the valve heaters. At 240v, the valve heaters were 6.87 Volts. So, we needed to drop about 0.5v. So, current would be 0.435 + 03 + 0.2 + 0.45 + 0.2 = 1.585 Amps. Using Ohms Law, R = 0.5 / 1.585 = 0.3 Ohms. The power it would dissipate is about 1.585 x 0.5 = 0.79 Watts. Time to look in my magic box. 3 off 1 Watt 1 Ohm Resistors. That’ll give us 0.33 Ohms and plenty power. The HT was still within tolerance for the valves, so I fitted these three resistors above the chassis, where the heat would be easier to dissipate and then tried the set. Sounded OK so I called it a day. I always do these little calculations when doing a job like this one. Best to know what you’re looking for before you dive into the …er….junk box! Nice looking set in the end.
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If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...? |
29th Feb 2008, 2:58 am | #2 |
Heptode
Join Date: Aug 2006
Location: Sheffield, South Yorkshire, UK
Posts: 990
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Re: (Let’s have some music) MAESTRO 756
Hello Steve,
That's a lovely looking set, reminds me a lot of the Bush VHF62, you've done a first class job of restoring too. Very well done! Your thorough description of lowering the mains supply is also excellent and a very useful reference for anyone wishing to carry out this modification on other sets that were intended for less than a 240v supply. First Class! |
29th Feb 2008, 11:07 am | #3 |
Nonode
Join Date: Jun 2004
Location: Norwich, Norfolk, UK.
Posts: 2,543
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Re: (Let’s have some music) MAESTRO 756
Well done Steve,
That's a very nice radio Regards David |
1st Mar 2008, 9:29 am | #4 |
Dekatron
Join Date: Nov 2003
Location: Near Leeds, West Yorkshire, UK
Posts: 4,609
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Re: (Let’s have some music) MAESTRO 756
Nice job, Steve - has a certain Grundigness about it!
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Mike. |
1st Mar 2008, 1:37 pm | #5 |
Retired Dormant Member
Join Date: Jun 2006
Posts: 1,798
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Re: (Let’s have some music) MAESTRO 756
Well done Steve, and the very name Bolton conjures up images of 'proper' engineering. Maybe a certain much missed steeplejack had something to do with it !
Geof |
4th Mar 2008, 9:07 am | #6 |
Nonode
Join Date: May 2005
Location: Godalming, Surrey, UK.
Posts: 2,593
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Re: (Let’s have some music) MAESTRO 756
Well done Steve ,
What a nice radio and I suspect the first Turkish built vintage radio on the forum. Howard |