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Old 24th December 2009, 06:20 AM   #21
VivaVee is offline VivaVee  New Zealand
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What is happening to the output voltage? It should stabilise at something like +260V* measured at pin 7 of V7 (6GC5). This can be measured at the positive terminal of C56 (8uF 200V - in the phono section away to the left) or at the positive terminal of C54 (1uF 200V cap in the power supply section)

Just for my clarification: it your preamp a SA5 or a SA5.1? That should be printed on the front panel and also on the serial number plate on the back.

*measured relative to ground.
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Last edited by VivaVee; 24th December 2009 at 06:21 AM. Reason: make my post clearer.
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Old 24th December 2009, 06:24 PM   #22
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Default Measuring Voltage

I have the 5.0. A very early model.

I could use some help knowing a good spot to use as ground for measuring?

Had you meant the voltage could "also" be measured at the other two mentioned locations?

Many thanks in advance!

Ed
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Old 25th December 2009, 02:09 AM   #23
VivaVee is offline VivaVee  New Zealand
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Quote:
Originally Posted by leviathon View Post
I have the 5.0. A very early model.

I could use some help knowing a good spot to use as ground for measuring?

Had you meant the voltage could "also" be measured at the other two mentioned locations?

Many thanks in advance!

Ed
The reason for asking abut the version is that the power/status indicator LED is driven differently in the two major versions.

A good ground would be the (-) terminal of any of the electrolytic caps in the power supply - they are big and blue!

And, yes, 'also' would have made it clearer
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Old 25th December 2009, 03:14 AM   #24
Pars is offline Pars  United States
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A good resistor for replacing these that isn't too expensive are the Mills MRA-5s. Supposedly 5W non-inductive wirewound. These will fit in place of the Rodersteins without any creative lead bending, etc.

As for the resistors in parallel with the CRD can (Siliconix CR-160 or equivalent), my SA5.1 has a resistor in series with it (before the CRD, assuming I traced the circuit out correctly), but nothing other than the 1N5378 91V zener in parallel with the CRD. Not shown on the schematic I have (which is an SA5, not 5.1 schematic).

I attached a diagram I had done of this at one point, as well as a pic of what this section in mine looked like.
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File Type: jpg SA5_zener.jpg (16.3 KB, 294 views)
File Type: jpg HiVreg.JPG (120.3 KB, 291 views)
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Old 25th December 2009, 04:09 PM   #25
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Thanks for the clarifcation. Am anxious to get in there with my DVM! We are hosting Christmas, but after that am looking forward to some quality time with my stereo!
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Old 25th December 2009, 04:24 PM   #26
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Pars, Thanks for the info. I looked at the Mills 5W at Partsconnexion. Couldn't find the values, though can likely mix and match. Will keep looking. Meantime I did order some stocking stuffers for my lads. Nothing like some silver hook-up wire to wake up to Christmas morning. At the same time I ordered some of the 1/2 watt Holco resistors. Found a 49K9 and 24K which should at least be better than what I have in there now.

Then on a ebay buying spree I purchased 23K7 and 49K9 1/4 W 1% 50PPM QTY 100 each SANNOHM RESISTOR. Not familiar with quality of these, and wattage on the low side, but they were on the cheap. Am building up quite a collection!
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Old 10th January 2010, 08:19 PM   #27
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Default So far so good...

- The 5651 strikes like a charm and when it is supposed to!
- Green led (looking dimmer?) not bothering me and may just be my imagination as stated before.

- Did change out the 49k9 with a Holco
- Changed out two 1K that looked a little weary in the outboard power supply
- Totally unsoldered cleaned, stripped and resoldered 3 wires (all ends) that were going to my quad of photoflash caps in the outboard power supply. Wires were pretty rough shape.

So am pretty happy. Haven't had chance to double check voltages yet. Still pretty busy around the house and at work. At least able to enjoy music while working at home.

Thank you everyone.
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Old 13th January 2010, 12:14 AM   #28
KBK is offline KBK  Canada
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Always be very careful when bending the leads of any Holco brand resistor. The end caps can delaminate from the resistive substrate and it can then also be intermittent. This potential failure issue is there with any resistor but it is especially noted for the Holco resistors.

Tube circuits have enough 'ghosts in the machine' when attempting to repair them, already. So, when bending the leads of a Holco resistor, always keep that in mind and support the lead at where it meets the body and then bend the lead. One way is to use two sets of miniature pliers.
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Old 14th January 2010, 09:06 PM   #29
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Default Holco Resistors

Thanks for the heads-up. I purchased a couple so have one on hand for back-up. Maybe I should have gotten a few more. So far so good with the one that I have installed.
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Old 21st January 2010, 03:16 AM   #30
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Default Hoping my measurements close enough?

Voltages readings are slightly different in the spots VivaVee suggested I test, but am hoping close enough...

Testing the 5651 tube per diagram VivaVee provided, I get 84 Volts versus the 85-86 Volts suggested

Testing pin 7 of the V7 tube to ground I get 251 Volts instead of 260 Volts suggested.

Hoping I'm close enough?

If done with this, or close to being done, what a feeling of self-satisfaction... of course none of which could be possible without everyone's help!!!

Next up would be a possibly DIY repair of my almost impossible to read Roksan Caspian CD display. An inherent problem from what I've read. Guess would have to jump over to the digital source forum.

Ed
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