Equipment with mixed technologies.

[FERNSEH]

Correction: Pye TT1. The EHT rectifier is in fact an EY51. Therefore there will be a good number of turns on the line output transformer for the heater winding.

DFWB.

[Cobaltblue]

Originally Posted by G6Tanuki

In the late-1950s there were portable 'hybrid' broadcast-radios that used the "96"-series battery valves for the RF/IF stages, and a couple of OC72 or similar transistors in push-pull for the audio output, a convenient way to reduce power consumption a bit compared to a class-A output valve.

The best known UK example of this is of course the Marconiphone P60B/ HMV 1410.

Cheers

Mike T

[FERNSEH]

Extract rom the circuit diagram of the Pye V700A "TransLantic" of 1961.
Transistor TR1 is the sync separator and V11B is the sync clipper and inverter.
Low level positive video developed across the cathode resistor of the video amplifier is supplied to the base of TR1 which conducts on the negative going sync tips. V11B inverts the positive going syncs which are developed across the collector load of TR1. So now we get the usual negative going sync to supply to the timebases.
Was the addition of the transistor sync separator worth all the bother, or again just something to keep the marketing people happy?

DFWB.

[kalee20]

Err... How about my washing machine, new in 2014?

Solenoid water valves, driven (I presume) by discrete MOSFETS controlled by a micro controller. Motor ditto. User interface is a thermionic vacuum fluorescent display, 2 colour, you can just see the filament glowing faintly!

[Peter.N.]

Yes, I appreciate that but was it worth producing an new valve for the sake of a couple of turns of wire, or did they use them in something mass produced?

If the TVette as a small transportable dual standard set, we had one of those when we got married.

Peter

[trsomian]

My parents had a black & white Grundig TV, dating from the late 60s at a guess, germanium transistors in the UHF tuner, at least one IC (I think two, but when I passed the set on working via this site a few years ago I naturally sent the circuit with it). I specifically remember that the audio detector and preamp were in an IC, which drove the driver transistor, which them drove the output valve. HT was half wave rectified mains via a diode valve, and the line output device was a valve. I seem to recall there were 4 valves, but I forget what the fourth one did

[FERNSEH]

Many hybrid TVs employed an IC for the line oscillator and a high voltage transistor to serve as the driver for the line output valve.
With regard to the Grundig TV, the fourth valve was most likely a PCL85/805 as the frame oscillator and output.
The Rediffusion Mark 13 mono TV employed only two valves, a PL504 and PY88.
Can't remember if there was any ICs in this model. Will check that out later.

Returning to the DY51 EHT diode. By using EHT rectifier diode with a low voltage heater means less turns for the heater winding which in turn reduces the risk of insulation breakdown. Usually a single turn loop on the line output transformer is all that is required for a 1.4volt heater.

DFWB..

[MrElectronicman]

I have just remembered that shorty after I moved to Canada a friend of mine gave me an RCA "Color" TV that was in sorry shape, I worked on it for a couple of months at least and finally got it working.
That set was a real mixture of technologies, it had the usual 7 and 9 pin valves, a couple of octal based valves, some compactrons with various numbers of pins, discreet silicon transistors, some rudimentary IC's, and a small metal rectifier or two.

[kalee20]

From a design point of view, hybrid equipment, I'm wondering what led the choice between valves and transistors for different stages?

I can appreciate the trusty PL504 etc for a line output stage, as the output device is a highly-stressed part. I can just about understand an audio output valve rather than a couple of power transistors, on grounds of cost, even allowing for the output transformer. But what about earlier stages?

The Marconi P60b radio used valves in early stages, transistors for the output. The Grundig TV in trsomian's post above, does it quite the opposite way round!

Transistors in a UHF tuner followed by valves in the IF stages doesn't make sense... as transistors with good enough HF performance existed, why not use throughout?

[ms660]

Maybe something to do with line output valve heater heater supply, valve audio doing something, equivalent dropper doing nothing as it were.

Lawrence.

[kan_turk]

Valved UHF tuners were notoriously insensitive and moving to transistors for the tuner only offered a cost-effective solution without a complete set re-design

[ms660]

As a blend of different bits...The Halolight, anyone remember them, a fluorescent tube around the screen, a Ferguson job, were there others?

Lawrence.

[trsomian]

Regarding the use of an audio output valve and the necessary transformer, I don't remember whether the Grundig set mentioned earlier had a headphone socket, but certainly the Panasonic colour set that replaced the Grundig had an audio output transformer to permit isolation of the headphone output from the live chassis electronics, albeit in the Panasonic instance driven by a single T03 transistor running in class A. Thus the Grundig may well have needed an output transformer, so why not drive it from a valve.

My parents also had an all valve Philips radio, that took the recording output from the loudspeaker winding of the output transformer, again, I assume for isolation reasons, because that was a live chassis set.

[G6Tanuki]

I recall at least one small valve/transistor-hybrid B&W TV in the 1970s that used a Class-A MJE340 transistor as the audio output stage, with around 160V HT - guess that was an easy "replace a valve with a transistor at the lowest cost" way to do it. Probably didn't even need a different o/p transformer compared to the valve version.

And from memory it also had a "LT" winding on the mains transformer that produced about 90V for the still-series-connected valve filaments and tube, as used in the older all-valve designs rather than the set using 6.3V-heater valves. I guess this was easier than converting to 6.3V valves and then needing service-operations to carry an increased range of spares.

[Synchrodyne]

Were there any equipments, particularly in the consumer field, that not only included valves (not counting CRTs), transistors and integrated circuits, but had both silicon and germanium transistor types?

The transition era for consumer equipment, from all-valve to all-solid-state, at say the 90% level, lasted approximately from the mid-1950s to the mid-1970s. During that time not only did solid-state devices replace valves, but silicon transistors largely replaced germanium transistors and integrated cicuits substantially replaced discrete transistors. So there were multiple layers of change, and some direct steps, such as valves to silicon transistors and valves to ICs.

Cheers,

[turretslug]

Some of the TV old hands here would know better than me, but I wouldn't be at all surprised if there were a handful of TVs of a particular period that featured germanium transistors along the lines of the AF239 in the UHF tuner, silicon devices in the vision IF strip, a scattering of relatively low integration ICs such as the TBA120 for sound demodulation and the "usual suspect" valves in timebase output duty.

[Synchrodyne]

Thanks! That prompted a quick search that brought up the Decca Bradford single-standard TV chassis as a candidate. The UHF tuner transistors are unidentified in the information I have, but are described as being of the low-noise PNP type. So there is a high probability that they were germanium, as silicon PNPs for the UHF job seem unlikely. The tuner was unusual in that although it was four-gang, as was customary for UK practice, it had a broadband input and triple-bandpass interstage rather than the usual single-tuned input and bandpass interstage.

The Bradford had BF19x silicon planar vision IF transistors, and an MC1351 intercarrier sound IC. The latter fed a PCL82 sound output valve from its demodulator output, its audio driver stage being unused (in which case why not use the MC1357?). So the sound signal path looks to have been germanium PNP, silicon NPN, silicon IC, then vacuum.

The Pye 691 single-standard TV chassis also had a similar mix, but differently deployed. The UHF tuner was silicon NPN, as was the IF strip. Intercarrier was handled by a TAA350 IC followed by a slope demodulator, then a discrete AF amplifier with a BC108, AC128 driver and AC128/AC176 complementary output. Valves were used in the luminance and chrominance output stages and timebases.

An interesting point here is that Mullard advertised its silicon planar transistors from about 1966, and the initial range did include the BF180 and BF181 for UHF TV tuners. There was a reasonably quick uptake of say the BF167 and BF173 for vision IF strip applications, but the established germanium PNP types hung on for a while in UHF tuners, with a relatively slow encroachment of the BF180 and BF181. To some extent that may have been inertia, in that UHF tuners were transistorized ahead of most other parts of TV receivers, and the makers were happy to leave existing designs in place whilst they worked on silicon planar IF strips, etc. But the carryover of germanium PNP types to second-generation colour TV chassis such as the Decca Bradford suggests that there might also have been performance and/or cost reasons for their retention.

Cheers,

[turretslug]

It's possible that some of the lingering germanium-ness in UHF tuners may have been down to the inertia of circuit convenience. The early UHF tuners tended to have one end of their tuning striplines directly soldered/brazed to the walls of the sturdy, five-sided box that provided overall screening, thus with the collector of RF amp tapped appropriately along the stripline, problematic UHF decoupling was avoided at least here. With the initial PNP transistors used,that forced negative earth technique with positive supply, suiting inexpensively if inefficiently dropper-derived supplies in hybrid sets.

When NPN transistors came along in UHF tuners, the reversal of polarity with this arrangement could result in the metalwork/case of this type of tuner assembly being at around +12V- that was OK for a tuner mounted on an insulating front panel with flying leads, but I'm sure I recall warnings in service sheets about avoiding metallic contact between tuner and main chassis. It was certainly prominent when attempting to use an ex-Philips 210 chassis multiband VHF/UHF silicon tuner with 30MHz receiver as IF! Once tuners became small, varicapped PCB tins with cheap ceramic chip UHF decouplers to isolate tuning lines, the problem went away.

Possibly another factor was that tuners tended to be a specialist, bought-in component rather than a part of a new TV design, so a good-performing germanium design may have tended to hang around over successive models, even when the in-house silicon IF strip was new.

[Maarten]

Output stages in small amplifiers such as used in record players, also tended to be germanium while the other stages used silicon transistors.

[Synchrodyne]

And there's more on germanium output devices in the silicon era in this concurrent thread: https://www.vintage-radio.net/forum/...380#post839380.

Cheers,