Transpro Type 862 Valve (Tube) tester. Help needed. - Page 1
Forum section: electronics / repair

author: clay1905
author_rank: Regular Contributor
timestamp: September 10, 2018, 06:56:05 am
content: Hello all,I'm on the lookout for any information on these valve testers. Copies of any publications, including but not limited to, instruction manuals, repair guides, schematics (oh! please yes) and especially copies of set-up cards. Using the set up cards, one can work backwards to what is at each socket when the controls are set in a particular way.Also, as is so often the case, this tester isn't exactly virginal. Some pre-my-ownership modifications have been made. One includes the cutting off of a pair of wires. Whence they came from I do not know. I'd like to put them back, or at least render them harmless. There will be some attached pictures, and here's the description:Looking at the chassis, there's a large rectangular capacitor pretty much directly behind the meter. Connected to said capacitor is one red, and two black wires. One black wire passes through a grommet and into an array of components on the right side. The other black wire is the one of interest. It pairs up with a red wire to form a twisted pair. Where do they go? The relaxed shape of the wires suggests that they may have connected somewhere near the diode, but I see no evidence of a broken or cut connection around there. Or any other place the wires could have reached to for that matter.In the first picture, you can see the red and black wires, the red coming through a grommet, the black from the capacitor. The second picture isn't that helpful, other than to show where the cut ends of the wires reach to, which might give an idea of their length. The red wire isn't going anywhere. It just happens to be in front of one of the rotary switch terminals.Another matter may be that the wiring colours don't appear to be very consistent across the years for this make of tester, so the actual colours might be different.If there's an owner of a Transpro Type 862 Tester out there, I would very much appreciate your having a look behind the main board to see where these wires go to. And of course, copies of any documents associated with the tester too.With Thanks,Clay.

author: drussell
author_rank: Super Contributor
timestamp: September 10, 2018, 12:30:08 pm
content: Did you take a look at:https://www.kevinchant.com/transpro.htmlNo schematic, though...

author: clay1905
author_rank: Regular Contributor
timestamp: September 10, 2018, 01:09:53 pm
content: Yes, I've found this page, as well as one at the Radio Museum. Neither has any technical information to speak of. Thanks for pointing to it though. You never know.I did download the Microsoft Word version of the manual, and have spent some time tidying it up, as well as adding a schematic for the 'adaptor panel' and the power connector.Otherwise, there seems to be a dearth of information on the web, just a few more pictures of the front panel. Hopefully there's an owner who'll stumble on this thread, and chip in with something helpful.

author: drussell
author_rank: Super Contributor
timestamp: September 10, 2018, 01:16:53 pm
content: Luckily tube testers are actually pretty simple wiring, though your unit is complicated by the fact that it includes a capacitor tester and voltmeter, etc. You may end up having to carefully trace everything out and draw your own schematic of it.Once we have a schematic of what is currently there, as well as where your disconnected wires are currently connected at the one end, where any modifications seem to have been made, etc., we can probably deduce how it was originally intended to be connected.

author: clay1905
author_rank: Regular Contributor
timestamp: September 10, 2018, 09:18:34 pm
content: Indeed, you're probably right here and some investigation is in order.One thing that has occurred to me is the mystery wires may be part of the power supply or associated wiring. The reason being a previous owner has cut off the original 5 pin plug from the internal wiring, and the original power cord has gone west. That and I can't see any terminal where a wire was once soldered inside the unit.There was both mains and battery operation. I have 7 possible wires that might be part of the power input and conditioning to follow up.Must away to work now, but this evening I'll have a further look.

author: drussell
author_rank: Super Contributor
timestamp: September 12, 2018, 01:40:21 pm
content: Quote from: clay1905 on September 10, 2018, 09:18:34 pmThat is my suspicion as well. This unit should have had at least two battery supplies of some sort in it. One, supposedly 6V supply could run the unit itself on battery via a mechanical vibrator DC-DC step-up converter in place of the AC line power. It would also have a voltage source for the resistance ranges on the VOM section. It appears that that was 3 x 1.5V flashlight cells of some unknown size.

author: clay1905
author_rank: Regular Contributor
timestamp: September 13, 2018, 10:21:07 am
content: I've had a little bit more of a look at the tester, and I find that the two mystery wires match up pretty well with the route taken by the 'known' power supply wires. The bends are very similar, and where the white 6 volt wires were cut off at different lengths, the red and black wires have the same length difference. Pretty good circumstantial evidence, methinks. Also, the other ends of the red and black wires lead towards what appears to be the board containing the range resistors for the Ohms scale.I'm not yet familiar with the construction style used, and it looks a bit odd to new eyes, so I'll put in some time there.According to the instructions I have, there was only one 6 volt battery. From what I'm seeing, there was a polarised supply as well as a non-polarised supply drawn from the one battery. I'm not that familiar with vibrators, but I'd imagine seeing it's 'making' AC, it wouldn't need a polarised supply, same for the diode filament. Following the supply to these shouldn't be too difficult.

author: clay1905
author_rank: Regular Contributor
timestamp: September 13, 2018, 09:32:38 pm
content: OK, I followed those mystery wires and in the end, without a serious dismantling one would never be certain where they go by that method. So I bit the bullet, and set the instrument to measure Ohms, then connected a 1.5V cell across the red and black wires.Sure enough, with the probe sockets shorted, the meter reads about quarter scale deflection.This is really good news. Now I've identified the power supply, and also I know the meter movement is working into the bargain. The DC volt scale also looks pretty accurate, at least in the low voltage range.Thanks Drussell, you've been a great help here. When you've got "L" plates on, there's nothing like being able to bounce ideas off somebody as you're feeling your way.