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 Valve Signal Generator
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 Return to top of page · Post #: 16 · Written at 10:27:24 PM on 17 January 2014.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 4467

A user manual would be handy also if anyone has one.

I provided the link in post #2.


 
 Return to top of page · Post #: 17 · Written at 10:55:51 PM on 17 January 2014.
Art's Gravatar
 Art
 Location: Somewhere, USA
 Member since 22 October 2013
 Member #: 1437
 Postcount: 895

Sorry GTC, when I read it the first time, I really only saw the word schematic,
didn't look at it at the time, but of course, noted your link is there for later.
I have printed it now for some bedside reading material ;)

It's a lot of grunt work to make it nice, some of which I can't do yet.
No use sanding yet without paint yet.
The front panel is aluminium, so that explains why it's still ok.

I'll leave this for now, and when I'm back I'll be ready to go with electronics,
I'm sure it can be nice again Smile


 
 Return to top of page · Post #: 18 · Written at 6:50:26 AM on 18 January 2014.
Scraps's avatar
 Location: Blue Mountains, NSW
 Member since 10 March 2013
 Member #: 1312
 Postcount: 401

GTC posted the link to the user manual in post #2. If you have trouble downloading let us know and it can be emailed.

EDIT, I didn't see the second page when I posted this.


 
 Return to top of page · Post #: 19 · Written at 5:05:51 PM on 18 January 2014.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3036

I am in the middle of another project on a different computer but actually have the book & original box for it.

Rod Champness did an article on those in Silicon Chip

I have a feeling mine had oil filled caps? These are very much like an electrolytic but have a cone on each end. They are about as reliable as wax papers & I refitted it.

Rather than stuff around. buy a pre fabricated, or use a good salvaged three wire cable and earth the chassis. "Regulations" basically state that metal that can become alive should be grounded anyway, and this qualifies.

With a small degree of modification you can use a gland, backwards (pointy end in) to secure the cable a lot more safely.

That plug seems to be some mongrel fitting. The case on mine was also tatty. I just cleaned it, stabilised it & painted it.

Those things have a very low (too low for my liking) B+ you will get away with decent 450V caps.

Marc


 
 Return to top of page · Post #: 20 · Written at 10:35:00 PM on 18 January 2014.
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 Art
 Location: Somewhere, USA
 Member since 22 October 2013
 Member #: 1437
 Postcount: 895

I don't know if IEC was standardised then,
or it was a fluke, but power cable problem is solved already:
Image Link
You just have to remove the little dummy panel, and the holes line up.
It's not going to be red, it's just a filler coat for sanding.. was rusty.

The plug and socket for the test lead is a bit of a funny one,
I like BNC better, but this isn't too bad, it does tighten the contact as the collar screwed in.


 
 Return to top of page · Post #: 21 · Written at 11:17:42 PM on 18 January 2014.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3036

I have a clone of that (Tech) all the same mistakes. That is one that I put an IEC socket on to solve a storage issue.

Yours will also be an after market Mod.


 
 Return to top of page · Post #: 22 · Written at 11:35:46 PM on 18 January 2014.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3036

The sine wave, to my mind, relates to the voltage on B+. I know not what they were thinking. The B+ value does not appear on the valve data sheet.

From what I interpret from the data sheet, the operating point of one of the two valves is right on the grid knee curve. That means that the half of the signal that falls below the knee will be amplified differently than the other half.


 
 Return to top of page · Post #: 23 · Written at 6:39:46 AM on 19 January 2014.
Scraps's avatar
 Location: Blue Mountains, NSW
 Member since 10 March 2013
 Member #: 1312
 Postcount: 401

I've been puzzling about this. The only thing the low setting does is switch in extra resistance. All resistors are in spec so maybe the extra resistance is dragging the voltage down just enough to put it below the critical level. I'll get back to this one day.

I just had a look at your IEC mod, it's a while since I've had my chassis out but from memory the holes in the chassis and case line up so the flex can be fed through the case. How will you get the chassis out (and back in) with the socket attached to the case?


 
 Return to top of page · Post #: 24 · Written at 1:44:48 PM on 19 January 2014.
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 Art
 Location: Somewhere, USA
 Member since 22 October 2013
 Member #: 1437
 Postcount: 895

Hi Scraps, You are switched on,
There may not even be room for the IEC socket.

A sneaky way would be to use washers and mount the IEC socket inside the chassis,
but I don't like that any more than you do.

Are the values for those death caps critical?
They are 0.001 MFD (102), but I can get 0.01 MFD (103) mains caps from Jaycar.


 
 Return to top of page · Post #: 25 · Written at 3:25:34 PM on 19 January 2014.
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 Art
 Location: Somewhere, USA
 Member since 22 October 2013
 Member #: 1437
 Postcount: 895

You're right, it can't work without hacking up the chassis inside,
right in a place where it screws to the cabinet too.

I'll just copy the way it was: Image Link


 
 Return to top of page · Post #: 26 · Written at 11:19:47 AM on 21 January 2014.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 4467

Are the values for those death caps critical?

It's probably best to stick with the original spec. The job of these caps is to keep any RFI on the mains out of the generator.

I'm intending to use these:

http://au.element14.com/wima/mpy20w1100fa00kssd/capacitor-class-1nf/dp/1006063.


 
 Return to top of page · Post #: 27 · Written at 1:54:04 PM on 21 January 2014.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 602

Would those ferrite filters that the 240V cords of some monitors and small TVs do the same job as the death caps?


 
 Return to top of page · Post #: 28 · Written at 4:25:30 PM on 21 January 2014.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3036

A little chopping changing for the IEC. Death caps do not filter the same as a Ferrite. Ferrite is high frequency.

If you don't want the cabinet live, earth the chassis. and use mains approved caps. 275VAC

Marc


 
 Return to top of page · Post #: 29 · Written at 7:09:09 PM on 22 January 2014.
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 Art
 Location: Somewhere, USA
 Member since 22 October 2013
 Member #: 1437
 Postcount: 895

Ok, I have just disconnected them for now, and have tested it sending music to a radio ok.
It needs some amplification at the input to the generator, but then it's ok.
The 400Hz and 1kHz tones don't work, I guess a few more caps need changing.
I do get a carrier though, when either of those tones are selected.


 
 Return to top of page · Post #: 30 · Written at 9:09:49 PM on 26 January 2017.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1089

I have just received one of these babies and my question is what is a " Y Cap " would the normal yellow 600 volt caps I use in my radios do the job . If not then why?

This looks to be a interesting little project.


 
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