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Old 8th Oct 2010, 7:09 am   #1
chokesrule
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Default 220v/240v Rectifier problem. Villingen 125

Hi, I am sorry about posting what must seem like an inane question as there are plenty of similiar posts, but none of them "spell it out me". I am a little uncertain with electricity so like to make everything plain in my mind before I fiddle.

When restorers use a roughly 100ohm resistor on the mains cable to drop 240 to 220 (the prescribed input voltage on my saba), do you mean:-

1) Connect the resistor to brown live mains cable before the power switch, obviously making sure the hot resistor does not burn anything and the blue neutral has "no" resistor in series to it?

2) As the signal cable grounds connect to the chassis and all the valves begin with " E "am I right to conclude that in this radio the chassis is "NOT LIVE" and so when I fit three core mains cable to the radio I should connect the chassis to earth?

3) For the life of me, I can find no rectifier valve or solid state rectifier on this radio. All I can see is a single diode so what have I missed?

Thanks for reading,
Alan.

Last edited by Darren-UK; 11th Oct 2010 at 12:10 am. Reason: FSK, SKP.
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Old 8th Oct 2010, 11:08 am   #2
threeseven
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Default Re: 220v/240v Rectifier problem. Villingen 125

Your questions are a little confusing.
Why would you want to use a mains dropper on a set with a mains transformer with selectable primary tappings for the appropriate supply voltage ?
The set does not have a valve rectifier, the diode you have found is the half wave mains rectifier.
E valves do not necessarily mean live chassis, and in this case the chassis is mains isolated by virtue of the transformer. The chassis will be at earth potential.

So all you have to do is set the transformer tapping at the closest to 240 volts and use it !
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Old 8th Oct 2010, 11:29 am   #3
peter_sol
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Default Re: 220v/240v Rectifier problem. Villingen 125

The Saba radio is for continental 220 volts so may need tapping down with the resistor.
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Old 8th Oct 2010, 12:19 pm   #4
threeseven
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Default Re: 220v/240v Rectifier problem. Villingen 125

Ooooops !! Should have read more slowly !
Well in that case you have probably been advised to use an auto transformer as the preferable solution, but if you still decide to go for the resistor method just install it inside the radio in a ventilated location, after the mains switch in the live side to the transformer primary. There will be no change to the chassis potential.

Also, in my haste I made another typo in my first reply, should be supply rectifier not mains rectifier.
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Old 8th Oct 2010, 3:37 pm   #5
Mr Moose
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Default Re: 220v/240v Rectifier problem. Villingen 125

Hello,
Looking at the pictures here http://saba.magnetofon.de/showtopic....3408&pagenum=2 (scroll down to the pictures), it should have a Siemens selenium rectifer: these often fail so it may have been replaced by a single silicon rectifier diode. It is usual to add a suitable series resistance as well as the silicon rectifier as the silicon rectifier has a lower forward resistance than the selenium one.
This one is the picture with the selenium rectifier http://saba.magnetofon.de/bildupload/SNV30451.JPG
Please dont worry about asking what you may think is a silly question, we all have to start somewhere and we are here to help, (even if we do sometimes disagree on whats best!) , not to judge your ability. If you don't understand a reply just ask again for clarification. Its much better to be safe than sorry.
Yours, Richard

Last edited by Mr Moose; 8th Oct 2010 at 3:50 pm.
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Old 10th Oct 2010, 5:20 pm   #6
chokesrule
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Default Re: 220v/240v Rectifier problem. Villingen 125

Hi, I am listening to the Saba right now. The 100R ohm 5watt resistor has to go on the live wire "BEFORE the OFF/ON switch as from what I can make out from my limited knowledge, the switch is also a distribution point and feeds the silver rectangular transformers.

The radio is running of 220 bang on.

However, I am sure this is not the high quality sound the radio is capable off. It sounds very tinny, suffers sibilance and there is no depth to the music even on FM. In fact it sounds like all the radio frequencies are suffering from poor reception. I have moved the unit around, added a better antenna but no joy. The volume is very very strong but I can hear in the background the hum of the transformer, especially on any frequencies not belonging to FM.

So I do not believe for one minute this radio is working to its potential, for there would not be all these people on here raving about them. I have replaced all the main capacitors with high quality ones, cleaned all switch/fuse contacts and valve bases/pins with deoxidiser, but now am at a loss to what to try next.

I have built some speakers from saba greencones for my hifi. I know what to expect from these superb greencones and the SRPP valve output stage. I put in a CD player and this is absolutely draw dropping.

Last edited by Darren-UK; 11th Oct 2010 at 12:07 am. Reason: FSK, SKP, spelling etc.
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Old 10th Oct 2010, 9:34 pm   #7
chokesrule
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Default Re: 220v/240v Rectifier problem. Villingen 125

I had not fixed the chassis into the cabinet by the 4 screws underneath the radio. This has removed the tinniness and improved the sound drastically. The hum is still there but is deeper sounding. It can now only be heard at low volume or no volume. I can live with it.

Last edited by Darren-UK; 11th Oct 2010 at 12:02 am. Reason: Sticking full-stop key problem fixed.
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