B9A valveholder query - UK Vintage Radio Repair and Restoration Discussion Forum

Ian - G4JQT · 23rd Nov 2018, 1:35 pm

Just finished a transmitter project (60m AM) and used some NOS B9A valve holders.

They all have a small dome or raised centre piece, so from the side the valves don't look fully seated. They're perfectly OK but just wondered what the purpose of such a design is. Other valve holders are flat, so the valves sit snugly down. Any ideas?

Thanks,

Ian

G8HQP Dave · 23rd Nov 2018, 2:23 pm

Just a guess: it avoids the socket for each pin pressing right up to the glass and potentially cracking the glass by sideways force. Other types of valveholder sometimes achieved this by the sockets having plenty of room to float in the moulding, or by the end of the socket being rounded outwards.

Boater Sam · 23rd Nov 2018, 3:07 pm

As Dave says but also more importantly it allows some airflow to cool the valve button base.

kalee20 · 23rd Nov 2018, 7:04 pm

McMurdo made their valveholders like this. I've often wondered, too!

Ian - G4JQT · 23rd Nov 2018, 7:41 pm

Thanks for the info everyone. It crossed my mind about the heat/air circulation aspect, but why wouldn't it be a standard if it was an advantage?

Anyway, there are all sorts of minor differences between manufactures, this is just another one I guess. It wasn't until after I wired them all up and put valves in that I noticed, and wondered if they'd been made for a specific job. Seems not.

Ian

23rd Nov 2018, 1:35 pm	#1
Ian - G4JQT Octode Join Date: Jun 2004 Location: Reading/Fakenham, UK. Posts: 1,326	B9A valveholder query Just finished a transmitter project (60m AM) and used some NOS B9A valve holders. They all have a small dome or raised centre piece, so from the side the valves don't look fully seated. They're perfectly OK but just wondered what the purpose of such a design is. Other valve holders are flat, so the valves sit snugly down. Any ideas? Thanks, Ian Attached Thumbnails

23rd Nov 2018, 2:23 pm	#2
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: B9A valveholder query Just a guess: it avoids the socket for each pin pressing right up to the glass and potentially cracking the glass by sideways force. Other types of valveholder sometimes achieved this by the sockets having plenty of room to float in the moulding, or by the end of the socket being rounded outwards.

23rd Nov 2018, 3:07 pm	#3
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: B9A valveholder query As Dave says but also more importantly it allows some airflow to cool the valve button base.

23rd Nov 2018, 7:04 pm	#4
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,088	Re: B9A valveholder query McMurdo made their valveholders like this. I've often wondered, too!

23rd Nov 2018, 7:41 pm	#5
Ian - G4JQT Octode Join Date: Jun 2004 Location: Reading/Fakenham, UK. Posts: 1,326	Re: B9A valveholder query Thanks for the info everyone. It crossed my mind about the heat/air circulation aspect, but why wouldn't it be a standard if it was an advantage? Anyway, there are all sorts of minor differences between manufactures, this is just another one I guess. It wasn't until after I wired them all up and put valves in that I noticed, and wondered if they'd been made for a specific job. Seems not. Ian