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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 7th Jul 2020, 4:47 pm   #1
stevehertz
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Default What is this valve like creature?

I found this unit in a box of valves. It has an octal base which is marked on the underside, 'McMurdo' and 'British made'. The unit itself is marked, SIMET, SRA/1/1600, W.E.R./TC.

Is it some kind of SS valve replacement or an industrial equipment module of it's own type?
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Old 7th Jul 2020, 4:48 pm   #2
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Default Re: What is this valve like creature?

Relay?
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Old 7th Jul 2020, 4:49 pm   #3
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Default Re: What is this valve like creature?

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Relay?
Yes, you're probably right Paul. Let's see what people say.
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Old 7th Jul 2020, 5:13 pm   #4
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Default Re: What is this valve like creature?

Not sure if this is any use but apparently SIMET was the rectifier division of Plessey.

Lawrence.
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Old 7th Jul 2020, 5:16 pm   #5
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Default Re: What is this valve like creature?

It's just possible it is a solid state plug in rectifier to replace the valve in power supplies. They were very popular in the USA but '1600' may be the resistance of a relay coil. Just a guess John.

Crossed!
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Old 7th Jul 2020, 5:20 pm   #6
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Default Re: What is this valve like creature?

Is that base octal or 11-pin?
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Old 7th Jul 2020, 5:37 pm   #7
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Default Re: What is this valve like creature?

I think McMurdo just made the octal plug blank that others like SIMET (?) incorporated into things. (Some years ago I ordered 2 from John Birkett as part of a bigger order, he invoiced for 2 but included a load more as I think he was fed up of the sight of them....). The "1600" could be a PIV rating? Quite a few folk made this sort of thing as a substitute for IO thermionic rectifiers, I recall some with a glass GT envelope and several top-hat diodes in a Paxolin support, all coated in a cherry-red varnish.
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Old 7th Jul 2020, 6:18 pm   #8
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Default Re: What is this valve like creature?

It looks very much like a silicon replacement for a valve rectifier. Try metering for diodes between the pins, using a few rectifier pinouts (5U4 and others) for reference.
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Old 7th Jul 2020, 7:03 pm   #9
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Default Re: What is this valve like creature?

Looking at the bottom of the base there appears to be three pins that have solder in them, the others look empty. They could be soldered at the top of course..

But if that's the true case then it's looking like a SPDT relay.
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Old 7th Jul 2020, 7:06 pm   #10
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Default Re: What is this valve like creature?

I'd be seeing it as a solid-state plug-in rectifier too; I used a load of these [made by US 'International Rectifier'] in the 1980s to replace the rather-longer-bodied-and-aluminium-canned jobs fitted in legacy Pye VHF base-stations [the rack-mounted ones with a QQV06/40A as the PA, and first-generation transistor receive-strips based on the old AM/FM Vanguard/Cambridge series]. The original octal-based aluminium-canned BY100 diodes served well for 30 years, but heat and transients eventually killed them.

I'd do some probing pin-to-pin and see what the various forward/reverse resistances are!
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Old 7th Jul 2020, 8:21 pm   #11
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Default Re: What is this valve like creature?

Gardners did some cans-on-octal jobs with microphone and 600 Ohm line matching transformers in them. Mumetal cans with a slightly browny silver hammer paint.

David
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Old 7th Jul 2020, 9:06 pm   #12
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Default Re: What is this valve like creature?

Come to think about it, it was in its valve base that I had to prise it out of. There were the remains of wires on some of the solder tags, so I'll check which ones they were and then take some resistance readings between the corresponding pins on the unit itself.
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Old 7th Jul 2020, 11:29 pm   #13
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Default Re: What is this valve like creature?

I've got a CV7136 which is an Octal based rectifier with 4 independent 400V 700mA diodes so it's not an exact substitute for a valve rectifier.

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Old 8th Jul 2020, 6:49 pm   #14
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Default Re: What is this valve like creature?

Pins 4, 6, and 8 have been used on the device's valve base. So, taking resistance readings on the device, pin 8 appears to be the junction of two diodes and pins 4 and 6 are connected to the other ends of the diodes. Using a digital meter the diodes read 153k and 156k respectively (infinity in the other direction) and using an AVO 8 on 'ohms' the equivalent readings are 4k and infinity. Why such a big discrepancy between the two meters?
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Old 8th Jul 2020, 7:20 pm   #15
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Default Re: What is this valve like creature?

Impedance of the digital meter much higher than 20K per volt of the Avo8.
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Old 8th Jul 2020, 7:56 pm   #16
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Default Re: What is this valve like creature?

It`s a solid state 5 volt rectifier.

When you measure diodes you are measuring forward voltage drop, not resistance so different meters give different results - nothing to do with the ohms per volt. Most digital meters give an actual indication of the volts drop - AVO's don't, but the normal semiconductor junction measurement is nevertheless consistent.
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Old 8th Jul 2020, 10:59 pm   #17
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Default Re: What is this valve like creature?

Quite a few DMMs have a "diode test" feature- this is a much more useful function for, um, testing diodes with than the "ohms" ranges, you quickly get a feel for whether Si, Ge etc. junctions are likely to be in good shape or not, many provide enough test voltage to check LEDs as well. (They've saved me a fair dollop of time, sweat and tears going through in-situ semiconductors in DC-coupled oscilloscope and audio amplifiers, too!). With semiconductor junctions, ohms ranges are very dependent on the test voltage used and the meter circuitry arrangements as to what kind of indication they end up giving, presumably the digital meter has a 9V battery, i.e. comfortably turning the diode junctions on and swamping any slight variations between them. Even a 3V type would be more helpful than an analogue meter with a 1.5V cell. I wouldn't be surprised if these high voltage valve rectifier substitutes have a couple of diode junctions in series in each leg to get the PIV, in which case an AVO on "ohms" using the 1.5V cell will only just be turning them on, giving sketchy results. The "ohms x 100" range with its 15V battery is likely to be more useful here.
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Old 9th Jul 2020, 12:15 pm   #18
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Default Re: What is this valve like creature?

The first post in this thread shows a DMM's Diode Test function in action:-

https://www.vintage-radio.net/forum/...ad.php?t=42194
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Old 9th Jul 2020, 12:49 pm   #19
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Default Re: What is this valve like creature?

Quote:
Originally Posted by Station X View Post
The first post in this thread shows a DMM's Diode Test function in action:-

https://www.vintage-radio.net/forum/...ad.php?t=42194
Yes I've got a multi-function transistor tester that I never thought about using and it shows two diodes connected to pin 8.
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Old 9th Jul 2020, 4:28 pm   #20
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Default Re: What is this valve like creature?

Looks like two silicon diodes in series each side.
 
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