Dynatron TRV14 Pathfinder.

[MALC SCOTT]

Hi, i have restored this radio which is working very well. On the front there is a control which rotates the internal ferrite aerial. This works OK, but when I leave loose of the control knob it returns to the original position. Has anyone got one of these sets to check this function? Cheers, Malc.

[Station X]

Is it standing on a level surface? Is there a friction brake which needs adjusting?

[MALC SCOTT]

Yes it is on a level table, no sign of any brake.

[crackle]

Maybe the wires to the aerial coils have stiffened with age and are working a little like return springs.
I dont know this radio but is it possible to fit a rubber grommet onto the shaft which rotates so it causes friction on the bracket?
Mike

[simpsons]

Any chance of a photo of the front panel and insides?

The model number you quote isn't showing up when Googled and any advice is a little difficult. Often, a chassis is used in a number of radios or radiograms and the photo might help.

Chris

[ms660]

It's TRV-14, external pics on radiomuseum, only one internal pic on Google pics so far as I can see and that doesn't reveal much.

Lawrence.

[Station X]

Thread title updated.

[simpsons]

Try as I might, I cannot find a Dynatron radio or radiogram with a rotatable ferrite rod aerial. The nearest set with the text "aerial" as a user control refers to the SW aerial trimmer.

Please prove me wrong with a photo.

Chris

[Synchrodyne]

I have some pictures that I downloaded from somewhere quite a while back, and so probably should not repost. These show the front panel with aerial control knob the middle one (of three) on the right-hand side. An overhead view of the chassis shows the ferrite rod above the main chassis, towards the right-hand side, with left-to-right orientation and in part above the FM front end sub-chassis. But there are no obvious signs of linkage between the aerial control knob and the aerial itself. Presumably the latter is mounted so that it can rotate somewhat on its yaw axis.

The TRV14 Pathfinder was presented as a new model in the 1960 Radio Show catalogue, with the comment: ‘A new and exciting table model incorporating the latest Dynatron A.M./F.M. tuner unit. Here is a table model made as they “used to be”.‘

That might have been something of an exaggeration. I think that the AM-SW side (only 2-gang, no RF amplifier, yet coverage to 25 MHz!!) would be found noticeably wanting when compared with say the Ekco A182 or the earlier Dynatron T10A tuner, let alone the Dynatron T139 tuner/control unit used in the last iteration of the Merlin receiver. The FM side was probably similar to the FM side of the T10 (which also has a single-valve front end) but perhaps not the T10A, which as best I can determine, moved up to a 2-valve front end. The single-ended output was also short of the push-pull norm for radio receivers as they used to be made.

I’d guess that TRV14 indicated Table Radio with VHF, circuit iteration 14. Dynatron had previously used RV12 for its VHF-only Ether Minstrel console radio receiver, so presumably it wanted a “T” prefix to differentiate the table model. It had reset its suffix numbers, starting at 10, with the Ether Pathfinder assembly of 1955, including the T10 tuner, TC10 control unit and LF10 amplifier. (The latter was of 12 watts output and might have been based upon the Osram 912 circuit – I’m not sure.) The “Pathfinder” name was presumably a link back to the Ether Pathfinder sequence of models from post-WWII through the mid-1950s, and which used the T69 then the T99 series of tuner/control units.

It was an apparent coincidence that about a year after the TRV14 was introduced, Hacker, with its Dynatron heritage, released the first iteration of its Mayflower FM-only table radio receiver with the model number RV14. (I am inclined to think, perhaps fancifully so, that the name “Mayflower” represented a metaphorical sailing away to a new land where the old strictures in respect of quality could still obtain.)


Cheers,

[Paul_RK]

Originally Posted by Synchrodyne

I’d guess that TRV14 indicated Table Radio with VHF, circuit iteration 14.

Yes, that seems right: the series continued, and as far as I know ended, with the TRV15, a 1966 mains-powered table set derived from the Atlantis transistor portable.

I have a TRV15, but haven't seen inside a TRV14. Mike's suggestion in post 4 looks well worth investigating. The only simple guesses occurring to me are that either there was designed to be more friction than there now is in the aerial rotation arrangement, or, more likely, the rod is being pulled to a certain orientation by wires whose insulation has stiffened over the years.

Paul

[sabaman]

Hi Malc,

TRV14 aerial cord winding instructions attached.

Hope this helps.

Seth

[sabaman]

Malc,

More information on aerial drive cord replacement.

For Synchrodyne and others like me who are interested in quality AM reception, this page of the service manual also indicates the IF bandwidth of this receiver.

I bought my TRV14 thinking the AM section was going to be better than usual. Unfortunately not so - it's rather average as Synchrodyne alludes to but it's a rather nice radio all the same.

Cheers,

Seth

[Synchrodyne]

That AM bandwidth, ±4 kHz, is about what I had expected for a single-selectivity receiver of the early 1960s. It was quite a come-down from previous Dynatron AM practice, where 4-position selectivity, with nominal bandwidths of ±2.5, ±5, ±7.5 and ±10 kHz had been the norm. Also, I think that an RF amplifier had also been used on most, if not all AM tuners. For the “short” versions, such as the T57 and T11, one of the two IF amplifiers was subtracted, making for a one RF, one IF circuit, which made a lot more sense on SW than the no RF, two IF configuration of the TRV14. I suspect though that the latter was an exercise in convenience, in that with a three-stage FM IF, the valves were already available for a two-stage AM IF, whereas an AM RF amplifier would most likely have required another valve.

Still, as the TRV14 was a table receiver it is probably more appropriate to compare it with other table receivers, and not with radiogram systems or console receivers. On FM a suitable comparative group would probably include the Pye FenMan II, Ekco A274/A277, Bush VHF64 and in particular both versions of the Hacker Mayflower given that they were contemporaries. On AM MW and LW, receivers like the Pye Fenman II and Bush VHF64 might be appropriate candidates, given that they were also aimed at the top end of the FM-AM table receiver market. For a representative higher level of AM MW performance than any of these were likely to provide, perhaps the older Murphy A186 (with variable selectivity) would be suitable reference.

On SW it might be harder to find a near-contemporary intended to provide about the same level of performance. Perhaps the Bush EBS64 would be appropriate – it was also of the no RF, two IF variety. The earlier generation of more highly specified export table receivers, including but not limited to the Murphy TA160, Pye PE80, Bush EBS44, Ambassador Viscount, and Ekco A182, all probably fell into a higher performance category.


Cheers,

[MALC SCOTT]

Hi, many thanks for the interesting replies. I have manually adjusted the ferrite rod aerial on its mounting for optimum performance where the radio is located. The radio has been fully re-capped and there were quite a number of the carbon resistors well out of spec. These have all been replaced. As I am going to use this set on a daily basis I have fitted it with a full set of NOS Mullard valves. The performance is very good, I just need one brass coloured insert for the on/off knob to complete it.

Cheers, Malc.