Lafayette HA-350

[cathoderay57]

Hi folks, I've been offered a Lafayette HA-350 receiver. I've downloaded a copy of the manual and it appears to be powered from USA 110-120v mains. Was there ever a UK version for 230-240v or am I going to have to use a step-down transformer? Cheers, Jerry

[Jon_G4MDC]

The manuals available online say 110-120V only and the transformer schematic shows only a single winding. Looks like you need the step down.

[Dave757]

Hi

In the past I had two HA350's, and they both ran from 250V.

Probably best to ask the seller.

Kind regards

Dave

[cathoderay57]

Thanks both. I'll get a look-see next week and will post the answer. Cheers, Jerry

[cathoderay57]

Hi folks, for the record mine has a mains transformer marked 117v so a step-down transformer it has to be, for now at least, unless I spot a reasonably priced compatible 230v job at RetroTech. Cheers, Jerry

[g0hze snowy]

I have a number of transformers recovered from old nixie test kit, 240v with 6.3v heater windings. If they are any good to you, just send me transformer sizes and i will see what i have, no charge for the item just cover the p&p

[cathoderay57]

Hi g0hze snowy, thanks for your reply. I have emailed Ed Dinning but if you have something suitable then happy days. The spec is as follows:

6.3v 3A
6.3v 2A
140-0-140v 110mA

The rectifier uses a pair of diodes returning to HT winding centre-tap, but I see no reason why I couldn’t use a transformer with a single 140v or 150v 110mA winding and a bridge rectifier instead.

The existing transformer is a drop-through measuring 75mm x 85mm x 60mm height above chassis. I could accommodate a slightly larger footprint but not by much.

Cheers,

Jerry

[g0hze snowy]

Hi Jerry
sorry but the transformers i have, have just the 1 x 6.3v winding, secondaries are either 1 x 230v or 2 x 120v, so dont think that they would do, however if you come up blank then i will look into it a bit more for you.cheers.

[Skywave]

It might be worthwhile removing the radio's covers and inspecting the wiring connections to the mains transformer's primary winding(s). It's not uncommon to find that such a transformer has two primary windings that can be hard-wired for 115 v. (Two windings in phase-parallel) or for 230 v. (Two windings in series phase additive).
We know (from posts above) that 115 v. and 230 v. a.c.mains requirement models were built. To me, seems very unlikely that two different transformers were used when these radios were built on the production line for export to various countries. (USA being predominantly 115 v. and Europe being 230 v.)

Al. / Sept. 22nd.

[Skywave]

Originally Posted by Jon_G4MDC

The manuals available on-line say 110-120V only and the transformer schematic shows only a single winding. Looks like you need the step down.

I'm quite surprised at that. I distinctly recall from the late 1960s the HA-350 being advertised in Practical Wireless (probably Henry's Radio); I nearly bought one when I was an avid SWL in those days. There wasn't any statement about a mains auto-transformer being required.
The on-line manuals might have been USA-sourced: hence, the 115 v. requirement.

Al.

[cathoderay57]

Hi Al, I restored a Lafayette HA-230 for somebody a few years ago and the mains transformer was dual-voltage exactly as you described. Sadly, my current HA-350 transformer has a single 117v primary with a tapping at 100v. Cheers, Jerry

[Skywave]

Jerry: the 115-v. only primary tells me that is was made for the US market (and, perhaps, part of Japan - which is dual-voltage). So, FWIW, it seems that some HA-350s were built with dual primaries and some with just one primary - which, in retrospect, does seem rather strange. However, perhaps the original market was the US only, then later, a market was also found in Europe. So, at that point, two markets: "Ah-Ha! O.K.: let's now fit dual-primary mains transformers!"

All very speculative, I know, but intriguing nonetheless.

Al. / Sept. 23rd.

[Granitehill]

Hi Jerry - many ages ago I had an HA350, bought new. It finally ended up as components in other projects, but I kept the mains transformer and mech. filter.
There was a dual voltage version - it had two 115v primary windings. I seem to remember the schematic had a label stuck to it referring to this.

I've just found the transformer. It was working when I removed it - you can have it for the postage costs if you want (1.84Kg).

[cathoderay57]

Hi John, that's brilliant, yes please. You have a P.M. I have run the set up on a step-down transformer and its performance is quite lively on 20m and 40m in the late afternoon. I wait to try the higher frequency bands in the morning. Some time in the past a mod was fitted to the S-meter circuit. According to the schematic the meter is supposed to be driven from the final IF valve cathode (V6). On mine it has a diode connected via a 30pF coupling capacitor to V6 anode that feeds a BC237 transistor and resistor network powered from the heater supply. The meter is controlled by the transistor collector current. It's not working at the moment and so I need to figure out what's going on. I'll do that first and probably revert the circuit to standard, before playing with the alignment, which might be unnecessary. Cheers, Jerry

[Granitehill]

It sounds like the transistor amp might be a bodge to get round a very low reading S meter?

Mine was anything but - the meter was very optimistic, and I added a shunt resistor across the meter to pull the calibration down to something more sensible. I set it as 50 microvolts for S9, and this was pretty level across the bands. It was actually the only (reasonably) believable S meter on any RX of mine. Definately one of the better features of the radio.

I'd guess the weird mod. points to a lot of loss in the IF stages - the mechanical filter would be prime suspect, I'd say (see my PM). When the set is 100%, there's possibly a bit much overall gain - the RF gain control is certainly needed.

[cathoderay57]

Hi John, that's useful, I'll have another crack at it this week. Cheers, Jerry

[cathoderay57]

The S-meter isn't working because the coil is open-circuit. I have posted a wanted ad. Cheers, Jerry

[cathoderay57]

Here are some pics of the radio, with John's mains transformer fitted. It now works fine off standard mains. I have removed the S-meter drive circuit modifications and reverted the circuit to standard. No meter yet (although I've ordered a Chinese 0-500 uA meter which won't arrive for a while) but I am getting about -2.0v to +2.0v at the meter terminals when I vary the zero-meter pot so looking better. Also the audio is less prone to overload on strong signals and the noise limiter is working as it should. The calibration oscillator doesn't seem to be working so more investigation needed. Does anybody know why there is a 10R series resistor in the heater circuit of the 6AL5 double diode detector/noise limiter? Hum reduction? Cheers, Jerry

[turretslug]

Some high-impedance thermionic diode circuits with cathodes that are "live" to audio can be very prone to hum resulting from stray loops of heater filament protruding from the ends of the cathode cylinder which are at high enough temperature to emit electrons, and comms receiver noise limiters are a classic example. One remedy is to slightly reduce the heater temperature with a series resistor- the cathode cylinder, being coated with an emissive potion of low work function, is less affected by this lower temperature than the plain stray heater ends. Later AR88s got this resistor in series with the 6H6 noise limiter's heater. Another remedy, notably adopted in many Eddystone sets, is to use a separate heater winding for the noise limiter diode which is elevated to a higher (positive) DC potential than the maximum AF excursion expected.

Colin

[cathoderay57]

Thanks Colin