|
Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
|
Thread Tools |
1st Jun 2021, 11:53 am | #21 | |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
|
Re: Mystery B9A valve
Quote:
[The TX I remembered was the KW 160 - it used a pair of 6BW6 in the modulator, not two EL84 as I had falsely remembered] |
|
1st Jun 2021, 2:04 pm | #22 |
Heptode
Join Date: May 2017
Location: Konongo, Ghana
Posts: 510
|
Re: Mystery B9A valve
Looking at these adverts in Practical Wireless (1958 & 1959) there does not seem to be much difference in price. But these are probably prices for end users, so not for producers of TV's.
https://worldradiohistory.com/hd2/ID...8-12-IDX-6.pdf https://worldradiohistory.com/hd2/ID...9-01-IDX-4.pdf
__________________
Robert |
1st Jun 2021, 3:30 pm | #23 |
Dekatron
Join Date: Nov 2003
Location: Fakenham, Norfolk, UK.
Posts: 4,246
|
Re: Mystery B9A valve
I must have been about 12 when I knocked together an audio amplifier with PL81 output, following a circuit in one of the magazines (hence about 1971). I wasn't up for metalwork, so built it on a repurposed perspex implosion screen, mounted on a lid removed from an add-on 78 rpm turntable: it just about worked. Looking online, several designs have employed the PL81 in audio roles, both single-ended and push-pull.
Paul |
2nd Jun 2021, 11:00 am | #24 |
Octode
Join Date: Mar 2016
Location: Knutsford, Cheshire, UK.
Posts: 1,488
|
Re: Mystery B9A valve
The PL82 is a nice valve for audio, much like an EL84 but needs 16V or so for the heater.
__________________
...where on earth did that spring/screw go?? |
2nd Jun 2021, 11:26 am | #25 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,191
|
Re: Mystery B9A valve
I have an old analogue XY flatbed recorder which uses a pair of PL82s in the servo amplifier for each axis. There is, indeed, a 16.5V secondary on each mains transformer to power their heaters.
|
2nd Jun 2021, 1:35 pm | #26 | |
Dekatron
Join Date: Sep 2003
Location: Near Swindon, North Wiltshire, UK.
Posts: 3,595
|
Re: Mystery B9A valve
Quote:
The circuit employed a Radiospares adjustable high power dropper resistor, an EF80 as the AF preamp and a PY82 half wave mains rectifier. All "live chassis" too, but with 20nF 750V capacitors isolating the input socket - I bet they're leaky now! Last edited by dazzlevision; 2nd Jun 2021 at 1:50 pm. Reason: Added text |
|
2nd Jun 2021, 2:34 pm | #27 |
Nonode
Join Date: Jun 2010
Location: Spalding, Peterborough, Cambridgeshire, UK.
Posts: 2,851
|
Re: Mystery B9A valve
I remember as a teenager copying some of the circuit for my 160M tx, but a transformer for the PL81 was too expensive for my schoolboy budget.
Then, around 15 years ago I acquired some used EL81, rememberithe use in hf tx. Not long after I bought a tx, I think it is the KW160, could be the Labgear one though. Buried behind some test gear at the moment, will need to dig it out sometime. A lot of used PL81 you see have the black tar like coating inside, but I think all my EL81 still looked clean. Rob
__________________
Apprehension creeping like a tube train up your spine - Cymbaline. Film More soundtrack - Pink Floyd |
2nd Jun 2021, 2:45 pm | #28 | |
Dekatron
Join Date: Nov 2003
Location: Fakenham, Norfolk, UK.
Posts: 4,246
|
Re: Mystery B9A valve
Quote:
Paul |
|
2nd Jun 2021, 4:43 pm | #29 |
Nonode
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 2,801
|
Re: Mystery B9A valve
EL81 was used in the Pye PTV which had mains transformer and earthed chassis, which
looked similar to the Pye TVT 2788 video monitor. I have some new in boxes, also EY88 (Philips Australia) indicating their use in the transformer set designs in that continent. |
4th Jun 2021, 6:18 pm | #30 | |
Pentode
Join Date: Dec 2005
Location: Denton, Manchester, UK.
Posts: 186
|
Re: Mystery B9A valve
Quote:
Very little background noise and multiple output choice including low impedance and 100v line. PPP PL81s might be the basis of an economic guitar amp? |
|
7th Jun 2021, 10:34 am | #31 | |
Dekatron
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,185
|
Re: Mystery B9A valve
Quote:
|
|