Truvox PD204 - info needed please!

[Ian 315]

Hi all, I received my latest Truvox tape recorder on Friday (some of you may have seen it listed on eBay). It was described as having no output, and having been down this road with a Truvox R104 I bought a while back, I immediately suspected open circuit heads. No surprise then to confirm this on unpacking it. What I need now is the specs for the heads - I suspect they're the same as the 100-series machines but want to check before going any further. I got the specs for the R104 from the original owner's instruction manual, but don't have a 200-series book. Anyone got that manual, and would they mind checking the PD204 specifications for me please?

Many thanks in advance, Ian

[MrElectronicman]

Hi Ian, I have a Truvox Model PD102 which I bought around 1965 or so.
I believe the 200 series of machines were almost identical except they used silicon transistors as opposed to the 100 series which used germainum transistors.

I have a service manual for the 100 series, but could not find any reference to the head spec.

The heads were made by Bogen and like yours one of the record heads has an open winding.

It was unfortunate that a few years ago I was using the machine and decided to to make a recording, but one of the channels was very noisy and the record meter was pegged out. It was caused by one of the OC45 transistors, but the time I found the problem and corrected it, the head was damaged presumably due to excess record current.

I did some research on Bogen heads, but with little success, also there were a couple of people that rewound and relapped tape heads, but they appear to all retired, like me.

[Ted Kendall]

I'm not sure that Bogens fail by excess current - enough of them have gone phut by now to imply that it's a consequence of manufacturing faults. I agree that the heads on the 100 and 200 series are the same - an issue of Tape Recorder, by coincidence, published circuits of both the 100 and 200, and the only difference was was 2G308s instead of OC44s and inversion of the power rail.

[Ian 315]

Hi chaps, thanks for your comments. I would think the open-circuit head problem was, most likely, a design/manufacturing fault, as it seems so common. Three of four windings (between the two heads) on my R104 were o/c and all on the PD204 are open.

Ted, thanks for the pointer to the magazine articles - the drive circuitry is near identical, so one could reasonably expect the heads to be similar too. I'll proceed on that basis and let you know how I get on.

By the way, for anyone else interested, it's the March 1969 issue of 'Tape Recorder' magazine.

Regards Ian