Hei bd,
since you are having so much fun with your Heathkit VTVM
I thought, I'll show you some photos of one of my four (don't ask
![Roll Eyes ::)](https://www.eevblog.com/forum/Smileys/default/rolleyes.gif)
) VTVM.
![Grin ;D](https://www.eevblog.com/forum/Smileys/default/grin.gif)
They are from Rohde & Schwarz, mostly made for the German Post
back in the 60's and 70's. They are called URU BN 1080 and are
heavy and sturdy as hell. The case is made of 1mm steel.
The vacuum tube used in them is a E80CC (double triode)
and I have four NOS of them here. I'd bought them just before
the prices were going insane, bloody audiophooles.
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/facepalm.gif)
I do have the original service manual as well,
see some pictures below. They were going through the effort
and did a schematic of every single operation mode.
I have added as an example the schematic for the "V-" operation mode.
So, let's start:
Front view:
![](https://i.imgur.com/TDwKoZT.jpg)
detailed view of the front:
![](https://i.imgur.com/ReHhJGX.jpg)
view from the top right to the vacuum tube:
![](https://i.imgur.com/Ni2LXR3.jpg)
nasty Selenium rectifier:
![](https://i.imgur.com/XBheWxY.jpg)
back side with the power transistor for the linear PSU, Germanium made:
![](https://i.imgur.com/wKGkWQV.jpg)
detail view to the PSU on the other side:
![](https://i.imgur.com/y8ef92p.jpg)
left side overview:
![](https://i.imgur.com/zyOqKoc.jpg)
left side, range selector switch:
![](https://i.imgur.com/RnoBcj8.jpg)
bottom view with some nice resistors, e.g. the 89 MOhm one:
![](https://i.imgur.com/pezCCrd.jpg)
And here is the manual, front page (isn't it nice? These silver letters ...):
![](https://i.imgur.com/bCu0iBG.jpg)
full schematic. I've uploaded the full resolution,
so it could take a little longer to download it. Same goes for the
other pictures of the schematic. These schematics were huge!
![Shocked :o](https://www.eevblog.com/forum/Smileys/default/shocked.gif)
![](https://i.imgur.com/gnQgCvd.jpg)
schematic example, operation mode "V-", left part:
![](https://i.imgur.com/gqlhKhN.jpg)
schematic example, operation mode "V-", middle part:
![](https://i.imgur.com/gflhM1p.jpg)
schematic example, operation mode "V-", right part:
![](https://i.imgur.com/CM0N0Nu.jpg)
some specs. This thing weighs 9kg!
![Shocked :o](https://www.eevblog.com/forum/Smileys/default/shocked.gif)
And you can overload every range by a factor of 100 with a max voltage up to 3000V
As bd139 said: "the tube goes only "meh" and carry on then."
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)
![](https://i.imgur.com/HQI66WG.jpg)
Enjoy!
Mounty
Edit: fixed stupidness caused by distraction
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/facepalm.gif)
Edit2: added some specs.