Tech Chat Servicing The FireBall Tuner
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There was a version of the Fireball tuner which incorporated coils for FM radio reception. Used in the Pam model 551FM. The tuner has an extended shaft to which the cam that operates the FM/TV switch is attached.
The HMV 1920 remote control TV set employs a motorised tuner, again the Fireball tuner is employed. like the tuner in the Pam 551FM the tuner has an extended shaft which is attached to the motor. The HMV 1920 was one of the earliest British made TV sets to incorporate an ultrasonic remote control system.
As a youngster "given things to play with" the first TV sets I was given had "Fireball" tuners in them - both were RGD 519s. This'd be mid-70s.
Interesting article. The KB Royal Star I have uses a fireball tuner and I've had to work on several of these before. The one in my set is working but there are some gain issues which are not attributed to the valves. The 6.8K was a frequent change but I wasn't aware of the 470K resistors going high. Difficult to change those so if they are still within tolerance, they are best left alone.
The Fireball tuner in the HMV 1920 employs a PCC89 frame grid valve as the RF amplifier. Frequency changer is a PCF80.
Posted by: @jcdaze
I always liked the fireball tuner. I just happen to have a spare one.
I got the impression from my late older brother that these were not liked in the trade. By the time I started servicing in 1970, there were very few left so I never formed an opinion. I got on with them OK but only worked on a few.
In Australia we saw the Fireball tuner in a few Thorn Atlas TVs in the early 60's. 6 volt valve heaters of course.
I don't recall any real issues with them.
Admiral (US) used to have a vaguely similar tuner. Not as compact as the Fireball.
Then there was that little Pye tuner that was sourced from the UK. We saw a lot of these because they were used in the number 1 selling TV in Australia in the 60's, the Pye Pedigree. The Pedigree was a "hero" design that saved the company. Because the channel changer knob was metal and was on the top of the TV, and because the valves were "buried" inside that tuner, the channel knob could get too hot to use! Pye released a modified knob with an insulator that fixed the problem.
I must admit that apart from cleaning the contacts on them that I never had to do any fault finding. To clean them, once the cover was removed and the retaining nut removed it was easy to clean the sprung contacts as well as the rotating contacts whereas in a turret tuner, if it was fully loaded, meant removing enough "biscuits" in order to do the sprung contacts as well. No big deal one way or the other really though.
As for the cleaning solution, Electrolube is mentioned in the article but I have used Servisol super 10 (a switch cleaner and lubricant). I am presuming it is much the same thing and as long as the cleaning solution contains lubricant, I guess it is ok.
Cleaning tuner contacts was a frequent requirement in those days. Lazy techs would lever a side cover away with a flat-blade screwdriver and insert the tube from a spray can. Not being in that category, I would unscrew the control head, remove tuner covers(s) and use silver polish (Silvo) in a 3 step process where the final step was a wipe of all contacts with CRC. This was a long-lasting fix.
NEVER spray contact cleaner into a tuner. It would de-tune particularly the local oscillator and frequently put the fine tuning out of range for a week or more until it dried out.
You didn't have to fix tuners much. Any tricky faults were handled by a changeover - there were firms that specialised in tuner overhauls. The company I worked for eventually set up a bench with a test jig just to do tuners when things got quiet.
Stock faults - 820k and 1m bias resistors in RF amps, a 4.7k resistor and a 22pf cap in Astor tuners, plastic parts associated with the preset fine tuning mechanisms. Mechanical wear. Cracked soldered joints on the PCBs in Pye tuners.
Those very compact Pye tuners were not actually made by Pye UK as I recall, they were some other brand. Does anyone know?
I don’t know who made the tuners, we’re they turret or incremental? Pye up to around 1963/4 used incremental type after it was a turret of some form. The Pye 11u chassis from around 1963/64 as used in Pye, Pam, Invivta, Ekco and Ferranti brands used the turret or push button tuners.
One type used in the Ferranti sets was from Philips and used printed circuit ‘biscuits’ for each channel. Another push button type was used by Ekco, not sure of the make but possibly made by Pye in their Lowestoft factory.
Perhaps the tuner you refer to was made at Lowestoft , they definitely made valve UHF tuners for the group.
The earlier Pye tuners were of conventional size and shape and used switch wafers in a conventional incremental design.
The one I'm referring to was quite small - about 80 x 60 x 40mm - and used a PCB with the valves nestled into the box. It was an incremental design but used a "turret" of 3 or 4 PCB discs about 30mm diameter with contact studs around the periphery and stationary wiper contacts attached to the base PCB. It was a clever and successful design.