Xtal Substitute Solution

[pwdrive]

Hi David, thanks for your take on all this, the R1155 does not really need an extra audio stage building for it either internally or externally just use 'phones, or, it will happily drive a standard single ended O/P transformer fixed into an external speaker cabinet unless of course you want to have it in "upset yer nieghbour" mode, as for the power supply then given the fact that the receiver is in what is basically an unvented cabinet then an external PSU is the proper way to go for best reliability.
I have no extra audio stage for my R1155 it drives a modern speaker via a single ended O/P transformer contained within the speaker cabinet very well. Yes sure it's a single conversion superhet but so was the legendary HRO although the HRO has an extra RF stage as compared to the R1155, the HRO and many others of that era will pickup what most later sets can..it's down to the aerial and the operator.
We have to remember that it was some of these early single conversion superhets (and even TRF's) that actually helped us to win the war.
Clearly these types of receivers were not meant for average domestic use I am not disputing that fact, but in my opinion the R1155 receiver was a good compact lightwieght clever design for it's time and it did what was asked of it.
As for the Bush DAC 90 I have to admit that I don't own one but have repaired a few in my time, again I would say the same insofar that it is compact lightwieght design and does what is expected when up to spec.
I think it can be a misunderstanding sometimes, because of the large numbers of these sets that were produced, the common as muck syndrome, which can sometimes can mask any design achievments and merits of the original design.
So...if anyone is reading this that hasn't got a R1155 or a DAC 90 etc but was toying with the idea, then I would say go and get one, when working up to spec there is 'nowt wrong with them.

Lawrence.

[pwdrive]

... and what about my poor old B28 and B40, assuming you're strong enough to get them on to the bench

Alan

All in all, bl**dy good sets as well so far as I am concerned.

Lawrence.

[Joe]

The trouble with both is the price, the 'Icon' effect, for what they are. I completely agree with David that the Murphy U198H is a better radio than the DAC90a, as is the Bush VHF90 or 70 if it comes to that, but is much cheaper.

I'd certainly like a B40 as well and these seem to go for more sensible prices. Collecting one and then putting it somewhere would certainly be a challenge.

There was a T1155 kicking about in one of that labs at college. Now that WOULD make a nice pantry Tx.

- Joe

[Yorkie]

CR100 anyone?

[pwdrive]

The trouble with both is the price, the 'Icon' effect.

I'd certainly like a B40 as well, tough putting it somewhere would certainly be a challenge.

- Joe

Hi Joe, yes the icon price and also the un got at price, that said you can still pick up a wreck of an R1155 for reasonable money if you look and wait either at auction or local or county amature sales, maybe two of them to make one good one, you can always flog off the surplus bits to get some cash back. The main chassis isn't that bad to work on, the RF box can be a bit of a pig sometimes but not insurmountable, biggest problem is usually the oil filled multi cap capacitor cans and the rubber covered wiring which would need renewing if it's gotten to the crumbly stage, restuffing the cap cans is no problem as they are fixed to the chassis at the base by a nut, if you carefully prise up the ally to get the inards out then prise it back down after then retightening the nut will fold it over the rest of the way and hide any screwdriver/pointed tool marks that might have been made in order to gain access to the can. In many case the slow motion tuning drive will need sorting out, they are quite easy to overhaul and get back to spec, the reduction ratio is excellent, one of the most commnn problems is the cork washer within the tuning drive it has usually "spread" over the steel disc which is part of the same mechanism or come adrift, the cork washer should be trimmed back if it has spread over the edge of the disc, trimmed back to the edge of the disc other wise the taper rollers will not contact the drum properly, full contact at the designated point is vital for differential rotational rate in the tuning drive, I am writing this purely from memory, there is much on the web about these receivers.
The other thing to remember is that the chassis is at a different potential to the HT -ve by approx 25 to 30 volts when the receiver is up to spec, you can earth the chassis if the PSU you use is transformer derived.
As regards the DF section then unless you are going the full restoration route it is not neccesary to get that section working, the receiver will work without it.
As you probably know many of these have been heavily modified over the years, some good some definately not so good so you would need to give it a good visual along with the circuit/layout diagram. Don't be put off by it's condition, it is like any equipement, one stage at a time. As previously said you don't need an added audio stage to use it, the PSU requirements are simple to fullfill.

Forgot to say, don't force any of the dust cores in the IF's or RF box, if they are stuck they will usually loosen up for alignment purposes by using various techniques also be aware that the BFO runs at half IF frequency I seem to recall.
Also forgot to say that the tuning drive as described above is for the original drive, later on they were sometimes fitted with a modified tuning drive, I have not encountered the later type but I guess someone hear has.

Lawrence.

[Joe]

I've been looking on e-Bay and see there are four PCRs on - one says it is "Very rare." They look to have plenty of room within to add a PSU at least.

It's the mechanical side of these high-spec things (though a PCR isn't that) which scares me more than the electronics. As you say though, information is available and time isn't an issue.

- Joe

[AlanBeckett]

CR100 anyone?

That's B28.

Alan

[pwdrive]

Hi again Joe, also forgot to say, the B40 series are thin on the ground compared to the R1155, if it's an auction job then you will almost certainly have to collect it one way or another they are not to massive they have a smaller footprint than say an AR88 but as you are probably aware, they are heavy at around 100lbs. I like the B40, quite reasonable to get at inside and perform very well, If doing a first time strip down of the tuning drive mech. either the dial drive or the capacitor drive or both then note everything down carefully, the full manual is a good one and is free somewhere on the web. Also note that the shaft on the tuning gang is ceramic and is a hard to find replacement item in the event of a f**k up in fact most dedicated B40 spares are in generall hard to come by.
Alignment (if needed) of the IF's is a bit more complicated than the norm due to the Xtal filter which I seem to remember is a two pole job in the B40, it's not beyond scope of the first timer though.
Ideally it should be done with a wobbulator/sweep generator and a suitable 'scope display, having said that I do not possess such instruments as yet but I have aligned many Xtal filters by ear or by using an analoge Avo meter connected across a suitable point, some comms sets are fitted with an "s" meter this can be used to align the xtal filter as well providing the rest of the receiver is up to spec and the signal level is kept low(ish) with these other methods it will not be theoretically perfect but it won't be far off once you have done a couple.
If going for a B40 series then I would recomend a later suffix one as they have an Osc Trim (Local Osc) control as a user control on the front panel and also they are rigged up for FSK reception, if no interest in FSK then you can adjust the FSK trimmers (which just shifts the BFO frequency) for upper or lower SSB corresponding to the settings of the function switch which can make things easier when switching the bands to tune in to the various SSB transmissions, most amature transmissions are LSB below 10 megs and USB above 10 megs, this general rule does not always follow though for aviation or military related or any other type of SSB transmissions.
Getting on to Shortwave reception opens up a whole new part of the hobby. Some of this you might know some you might not, whichever way good luck if you get one.

Lawrence.

[AlanBeckett]

Unfortunately the 'D' versions, with more modern valves, tend to go for much higher prices. Theoretically you could covert a 'C' to a 'D' at least as far as the valves are concerned.
The valves for the earlier versions are getting a bit thin on the ground, especially CV302/ECH22.
For SSB you really need Outfit FAZ - yes, I'll get to it. I've got the plugs and sockets now. They really are thin on the ground, and full of transistors.

Alan

[pwdrive]

Unfortunately the 'D' versions, with more modern valves, tend to go for much higher prices. Theoretically you could covert a 'C' to a 'D' at least as far as the valves are concerned.
The valves for the earlier versions are getting a bit thin on the ground, especially CV302/ECH22.
For SSB you really need Outfit FAZ - yes, I'll get to it. I've got the plugs and sockets now. They really are thin on the ground, and full of transistors.

Alan

Alan I reckon that FAZ unit you have is worth more than the B40, got me thinking now, I wonder if the RA218 converter I have would work with the B40, ie: knock up a simple outboard down converter to drop the B40's IF down to 100Kcs (the RA218's input frequency) I seem to remember that the B40's IF is 500kcs so no odd frequency to worry about, what do you think?

Lawrence.