Trio RS-6 (Wobbulator?)

[TonyDuell]

I bought a bit of vintage test gear (well, it's full of valves, even the HT and EHT rectifiers) this morning. It was made by Trio and the model seems to be 'RS-6'.

It looks like a small 'scope, in fact that's what the seller called it, but as it has a frequency control (turning a variable capacitor inside) which seems to cover the MW broadcast band on one range and has '465' marked on the other range (I assume 465kHz, the common IF frequency), I think it is more likely to be a wobbulator for aligning MW radios.

Does anyone know anything about it, manuals, circuit diagram, etc? Google has turned up nothing.

[WME_bill]

Can you give us a picture please. It may be a bit of badge engineering, and a picture would help suggest alternatives. wme_bill

[TonyDuell]

I think it predates the era of mass badge engineering. My guess (from the look of the chassis/panel) is that it dates from late 1960s/early 1970s. I can't see any semiconductors inside, for example, all valves. Even the supply rectifiers. A 6AC4 (EZ81) for the HT line and a DY80 for the -ve EHT to the CRT, which means the filament is connected to the end and tap of the EHT winding on the mains transformer and the anode (top cap) goes to the smoothing capacitor.

And that's as far as I've got with figuring it out..

Still, pictures can't hurt, but I am busy for the next couple of days so they will have to wait a bit.

[TonyDuell]

I've had another look at it and taken some photos. I'll try to get those uploaded in a few days time.

There is a subchassis alongside the CRT with 3 valves on it (2 off 12AT7, 1 off 12AU7) which I think are the deflection amplifiers. On the main chassis, as well as the PSU bits I mentioned above is a screened section which looks to be the RF oscillator. It contains the tuning capacitor and 3 valves (12AT7, 6BL8, 6EJ7). Outside that on the chassis are two more 6BL8's, a 6BE6, a 4.55MHz crystal and a pair of what appear to be voltage stabiliser valves, VR150MT and VR75MT. I haven't yet found any data on those but I assume 150V and 75V.

The CRT is a 3KP1(F) made by Hitachi.

[Terry_VK5TM]

VR150MT = OA2
VR75MT = OC2

According to the Japanese.
Actually, there is plenty of info/data on them, you just need to be able to translate the sites.

[TonyDuell]

Thanks. I would have guessed there were Western equivalents for them.

[Radio Wrangler]

The Trio Corporation made a number of pieces of test gear - power supplies, signal generators and oscilloscopes. Some of it was intended as single-purpose production line equipment like your wobbulator for AM broadcast receiver IFs. Some of it was intended for radio/TV repair workshops, and some of the later scopes sold into universities for their basic lab use.

All decent stuff and good for its purpose.

The 4.55 MHz crystal suggests that the 465kHz sweep is done with a swept oscillator in the 4 or 5 MHz region, mixed down by the crystal oscillator. This means that the swept oscillator need only tune by a very small percentage to help with linearity.

It'll be interesting to find out whether it has one semiconductor in it, a varactor diode to tune the swept oscillator. These were seen as a big improvement on reactance valves and worth their extra expense. So they found their way into equipment fairly early on. Fujitsu was big in Japan for these things.

The sweep itself could be mains-derived. A sweep oscillator would be a nice surprise otherwise today's crappy mains waveforms can be a problem. Japan's mains voltage had a pretty wide tolerance and a mixture of 50 and 60Hz areas, so you might be lucky.

AC coupled deflection amplifiers for scope tubes are a lot easier to do with valves than DC ones, so there likely isn't a detector in the measurement path.

An interesting find, and useful!

David

[TonyDuell]

Having looked around inside it there seem to be a couple of semiconductor diodes, but in the power supply. I haven't noticed one inside the oscillator screened can. I thought the 6EJ7 (==EF184) might be a reactance valve.

There is a 6BE6 (EK90 heptode) on the main chassis which could be the mixer for some kind of oscillator down conversion. On the other hand, the oscillator valves, variable capacitor, output attenuator and RF output connector are all inside a screening cover, the 6BE6 isn't. Perhaps one of the other valves (that 6EJ7) is the mixer?

I wondered if the crystal was for the 'markers' which can come from an internal or external source.

There is a 'blanking' switch and phase preset on the panel. I suspect this means that the thing uses mains-dervied sweep. I've not tried to trace any of the circuitry yet, I am still hoping for a manual or circuit diagram.

[TonyDuell]

I have attached some photos of this wobbualtor, and put rather more (at higher resolution) here :

https://www.***********/photos/tony_d...57701242122345

[turretslug]

That's rather a nice thing. Well done for acquiring it. Fingers crossed that it will indeed prove to be "very reriable" as those now somewhat toe-curling adverts used to say,

Colin

[Terry_VK5TM]

This is a long shot but there may have been a similar Kenwood instrument.

Not sure when Trio and Kenwood merged, but it wasn't unusual to see identical gear with either name on it in the 70's, maybe they had some arrangement before then.

[dazzlevision]

For many years, Trio was the name used for Kenwood (of Japan) products in the UK, due to the Kenwood name being a registered trademark for those famous and versatile British food mixers (e.g. Kenwood Chef).

[Andrewausfa]

I've seen pics of a Trio RS-4 while searching for the RS-6. There must be something out there.

Trio was the original Japanese company, their US importer/agent was called Kenwood. Trio later bought the agent out, dropped the Trio name in 1986 and re-branded themselves as Kenwood.

Andrew

[Radio Wrangler]

The Trio corporation was the name of the company. They sold equipment under the 'Kenwood' brand name in the USA, but they considered that there could be conflict with the Kenwood food mixer firm (Thorn eventually) already having that brand on electrical items. So in the UK they traded under their real name, Trio. After a time they decided that there was enough difference between kitchen appliances and radio/hifi stuff so they thought they could simplify their structure by putting everything under one brand, so they stopped badging stuff Trio for the UK and stuck Kenwood on instead.

In a parallel way, the Tandy corporation (registered in Fort Worth) was the firm operating franchised radio stuff shops branded "Radio Shack' in the states. But the Radio Shack name was already registered in the UK by an amateur radio dealer. So Tandy chose to trade in the UK under the parent company name, Tandy.

David