Circuit information on the Dynatron T99 does seem to be unobtainium. Some time back I checked with Savoy Hill, who did not have it, although they did have information on the T139, and also, I think, on the T69.
One could speculate that the T99 was perhaps a miniature-valve version of the T69, or a precursor to the T139, or perhaps somewhere between those two. Judging from the advertisement in Wireless World (WW) for 1952 September, the T99 tuner/control unit was introduced for the “1953 model year”.
The T139 tuner/control unit then appeared two years later, as advertised in WW for 1954 September. The major innovation was the addition of bandspread shortwave bands, something that had been featured on the top-of-the-range British export radio receivers for several years (e.g. Ambassador Viscount, Murphy TA160, Pye PE80 amongst others) and which also had appeared in the radiogram chassis (e.g. Armstrong EXP119) and hi-fi tuner (e.g. Chapman S6BS) sectors. The T99 and T139 appear to have had similar key features, such as four-position variable selectivity and a whistle filter. So possibly some core features of the T139 tuner circuit do read back to the T99. The T139 had an RF pre-stage (grounded grid, triode-strapped Z77 with untuned input) that was used on the higher HF bands, and which I suspect was not included in the T99.
The T99 does appear to have been used as the basis of a Marconi MIMCO marine broadcast receiver, as shown in the attached item from Wireless World 1953 August. The T139 was of course the basis for the MIMCO 2235A, which probably superseded the initial version and I think was much better known. The WW 1954 September advertisement shows that Dynatron was also offering “industrial” versions of the T139 in metal bench cabinets, and the MIMCO derivative could well have been part of that sequence.
The T139 was listed in the 1957, 1958 and 1959 issues of Hi Fi Yearbook (HFYB), but not the T99. Perhaps the latter had a relatively short production life?
After the T139, Dynatron appears to have turned to true tuners rather than tuner-control unit combinations, the first being the T10 FM-AM unit that was listed in HFYB 1956. Judging by the description provided in a WW 1959 March advertisement, the AM side of the T10 had inherited some of the T99/T139 features, such as 4-position variable selectivity.
Cheers,
P.S. I'll add the attachments when I figure out how to do it!
One could speculate that the T99 was perhaps a miniature-valve version of the T69, or a precursor to the T139, or perhaps somewhere between those two. Judging from the advertisement in Wireless World (WW) for 1952 September, the T99 tuner/control unit was introduced for the “1953 model year”.
The T139 tuner/control unit then appeared two years later, as advertised in WW for 1954 September. The major innovation was the addition of bandspread shortwave bands, something that had been featured on the top-of-the-range British export radio receivers for several years (e.g. Ambassador Viscount, Murphy TA160, Pye PE80 amongst others) and which also had appeared in the radiogram chassis (e.g. Armstrong EXP119) and hi-fi tuner (e.g. Chapman S6BS) sectors. The T99 and T139 appear to have had similar key features, such as four-position variable selectivity and a whistle filter. So possibly some core features of the T139 tuner circuit do read back to the T99. The T139 had an RF pre-stage (grounded grid, triode-strapped Z77 with untuned input) that was used on the higher HF bands, and which I suspect was not included in the T99.
The T99 does appear to have been used as the basis of a Marconi MIMCO marine broadcast receiver, as shown in the attached item from Wireless World 1953 August. The T139 was of course the basis for the MIMCO 2235A, which probably superseded the initial version and I think was much better known. The WW 1954 September advertisement shows that Dynatron was also offering “industrial” versions of the T139 in metal bench cabinets, and the MIMCO derivative could well have been part of that sequence.
The T139 was listed in the 1957, 1958 and 1959 issues of Hi Fi Yearbook (HFYB), but not the T99. Perhaps the latter had a relatively short production life?
After the T139, Dynatron appears to have turned to true tuners rather than tuner-control unit combinations, the first being the T10 FM-AM unit that was listed in HFYB 1956. Judging by the description provided in a WW 1959 March advertisement, the AM side of the T10 had inherited some of the T99/T139 features, such as 4-position variable selectivity.
Cheers,
P.S. I'll add the attachments when I figure out how to do it!
