Mimco Dynatron T99B

[Radio Tech]

Hi Folks

I have now acquired a Mimco Dynatron T99B Radio, this is the one with the protractor shape tuning dial, massive set but extremely heavy. I wonder if any member has a service manual for one of these or a copy of one so that I can get more associated with the circuit and layout.

Best wishes

Ken

[John Caswell]

Any chance of pictures please and I will see what I have.

John

[Radio Tech]

Hi John

Here is a picture of the set.

Ken

[rontech]

That is beautiful!

[simpsons]

From a post by Syncrodyne on this site (search Dynatron Mimco)


"I can’t help you directly; information for these units is apparently very difficult to come by.

I suspect that the Mimco 1155A designation applies to the complete receiver, which was a combination of the Dynatron T99 tuner/control unit and the LF512 amplifier. This was apparently the first version of the Mimco/Dynatron marine broadcast receiver. It was followed by the Mimco 2235A, which combined the Dynatron T139 and LF512A.

Coincidentally an amplifier which is apparently the Dynatron LF512(A) has come up in another recent thread, http://www.vintage-radio.net/forum/s...d.php?t=134931, which probably covers the very limited amount of information that is available."

Searching for the T139 and LF512A results in many posts and links, too many to detail here, which I hope will help.

Chris

[John Caswell]

Hi Kken,
Sorry I have been thru all my Dynatron blurb and have come up with nothing on the T99. I am sure it was the next variation of the T69 chassis as the tuning scale is definitely a T69D. Not having seen the chassis layout I guess it has the cylindrical IF transformers with directly adjustable ferrite cores as opposed to the later square ones with the cores adjusted via a 6BA metal screw thread, and B9A based valves. Schematics seem to be non existent for this chassis, although I do have some blurb on the T139 and LF512 which is just about readable. A note of the tuner valve lineup may help, although once again guessing at EF89 RF, ECH81 or X79 Freq. Changer, EF89 1st IF, EF89 2nd IF, EB91 Detect, EM34 Tuning Indic.
Please PM me if you think these may help.

John

[Radio Tech]

Hi John

I will check the exact valve line up for the set and let you know by pm, I have powered the set up but it lacks sound and this what I am having trouble with finding where it has gone wrong. The set uses the 1154A Tuner and 1155A Amplifier.

Ken

[Synchrodyne]

There is some information on the Dynatron T99 here:

Dynatron T99 Tuner (golbornevintageradio.co.uk)


The T99 was the apparent successor to the T69 series. Evidently it was advertised in Wireless World (WW) 1951 October as part of the “Ether Conqueror V” suite:




I haven’t found the actual advertisement – perhaps someone here who has it can post it.

Assuming that the “V” in Ether Conqueror V” meant five, the designation could be rationalized in that there were apparently four iterations of the T69, namely T69(A), T69B, T69C and T69D.

With the T99, Dynatron swung from Mazda 4-volt to Osram valves, miniatures in the small-signal section. The corresponding amplifier, replacing the LF59 series, was the LF612, a simple (unimaginative?) unit using triode-strapped KT66s.

An updated version, with T99A and LF612A, was advertised in WW 1952 October:





MIMCO seems to have adopted the Dynatron combination for use as a marine broadcast master receiver in 1953:




I think that was the “industrial” version with the LF512 amplifier, 6V6 output with a line-driving transformer.


Added to the Dynatron range in late 1954 was the “Ether Marshal”, which initially ran alongside the “Ether Conqueror”. This had the more elaborate T139 tuner/control unit paired with the LF613 amplifier, which was probably not too much different to the LF612. The industrial version used the LF512A amplifier, with the T139/LF512A combination used for the Mimco 2235A.




It would appear that circuit information for the T99 is unobtainium. Possibly an approximation to the T99 could be obtained by interpolating between the T69 and T139, service information for both being available. The T99 appears to have followed the T69 layout to a large extent, but may have been more like the T139 in the AGC and AF departments.

The T139/LF613 service data mentions the LF512A, and includes some data for it, but does not provide a schematic.

Some overall confusion arises because Dynatron used names such as “Ether Conqueror” both for the electronic chassis and for complete radiogram products. And some complete products used different electronics suites at different times. E.g. the post-WWII “Merlin” console radio receiver first went through the “Ether Conqueror” electronics sequence but was switched to the “Ether Marshal” when that became available.

I do not know whether Mimco switched directly from the 1154A/1155A (T99) to the 2235A (T139) when the latter became available, or whether there was some overlap. But the 2235A does seem to be the better known of the two.

The T99 and T139 seem to have been offered in parallel for a season, but the T99 looks to have disappeared in late 1955 when Dynatron introduced the “Ether Pathfinder” suite, T10/TC10/LF10. The T139 remained available though, its last Hi Fi Year Book listing being 1959. What Mimco did after that for a ship’s broadcast receiver I don’t know. Other makes of bandspread receivers (Armstrong EXP119 and BS125, Chapman S6BS) are known to have been used in ship’s entertainment installations, and there is some evidence that Mimco deployed the Marconi HR22 SSB receiver for that purpose, essentially following HF broadcast relay practice in which AFC-equipped SSB/ISB receivers, with broadcast-appropriate IF filters, were used to minimize selective fading distortion.


Cheers,

[Synchrodyne]

Originally Posted by Synchrodyne

There is some information on the Dynatron T99 here:

Dynatron T99 Tuner (golbornevintageradio.co.uk)

That web address should have come out as:

https://golbornevintageradio.co.uk/f...d.php?tid=5847


Cheers,

[Julesomega]

As I posted on the now closed thread, it probably was the Merlin - I was looking through the Dynatrons on Radiomuseum and they show the All Band Radio Tuner T99A which they say was used in the Merlin though they don't have that on their pages yet