GZ34/GZ37 pin 1

If they glow, this is the place to be
Post Reply
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#1 GZ34/GZ37 pin 1

Post by pre65 »

Hi-i have just printed the GZ37 pinout info to aid me wiring it up correctly and i am confused by the pin 1 connection.

It says "metalising internal,or external connection to the valve"

What does this mean ?
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
Lee S
Old Hand
Posts: 664
Joined: Fri Aug 10, 2007 9:39 am
Location: UK

#2

Post by Lee S »

Isn't metalising the internal or external screening that should be just left disconnected?
©2020 Lee
User avatar
Nick
Site Admin
Posts: 15711
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#3

Post by Nick »

Yes, anything marked ic should be left unconnected
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#4

Post by pre65 »

Hi-thats just as well as the GZ37 that i got from "Jibbles" a couple of years ago turn out to be 5U3C !

That said i think they will do what i need,and pins 3,5 & 7 are actually missing from the valve (no probs as they are not used).
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
andrew Ivimey
Social Sevices have been notified
Posts: 8307
Joined: Mon Jun 11, 2007 8:33 am
Location: Bedford

#5

Post by andrew Ivimey »

Hi Philip, that means that they are 5U4Gs. Directly heated, they have no slow start. They should be fine but if you want to be careful,perhaps you could use a separate 'standby switch' on the centretap of the main secondaries to earth. This would allow the heaters to warm through before HT roars through the amplifier.
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#6

Post by pre65 »

Hi Andrew-thanks for that info.

These were the rectifiers that did one of my Quads in !!

As a temp measure i could use the GZ32 s from the Quads,i must have slow start up.

What is the "best" GZ34 to get these days ?
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#7

Post by pre65 »

Hi-i have just checked the GZ32 s i got from "Jibbles" and they are 5U4C which are also directly heated !!!

I am afraid i wont praise him again.


So now in my rectifier arsenal i have a total of 6 valves (3 types) all directly heated.

BUM. :evil:
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
Nick
Site Admin
Posts: 15711
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#8

Post by Nick »

Why must you have slow startup? Whats the actual problem without it in this case?
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#9

Post by pre65 »

Hi-i was under the impression that slow start up was a good thing !

My 300b amp has a 2 stage on switch so you can get the valves warmed up before you switch the directly heated rectifier on.

Are you saying it isn't a problem Nick ?

I would,of course,rather use valves i have. :)
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
Nick
Site Admin
Posts: 15711
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#10

Post by Nick »

Yes, but there is slow and slow.

Its nice to get the valves warmed up before applying voltage, but in the case of 300bs, being directly heated themself's they would warm up at about the same rate as the rectifiers.

Normally the issues with slow start (other than valves getting HT before they are warm) include the voltage being higher than wanted because the supply is off load, and a badly damped supply ringing and causing a even higher voltage spike. Much of this is related to choke input supplies (for example) where the load needs to pull more current that the critical value.

But most of that problem is related to using solid state regs, ie, immediate start.

I cant help thinking that any design that relies on the various parts starting up when they are expected will eventually cause a problem.

For example, if the caps in the power supply are able to handle the voltage if the amp is off load, what happens if a fillament goes?
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#11

Post by pre65 »

Hi-as i have a separate 5V transformer for the rectifier filament could i switch this separately after the valve heaters have come on.

Will it harm a directly heated rectifier to have HT without the filament on ?
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
Nick
Site Admin
Posts: 15711
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#12

Post by Nick »

Will it harm a directly heated rectifier to have HT without the filament on ?
Don't know.

Try it and see what happens.

All I am trying to get at, is you are now adding another thing to fix a problem that is only a problem because you have read somewhere that it may be a problem in different circumstances.

I would try and answer the following questions to arrive at your solution.

1. What are the valves I am using, will they fail or suffer if B+ is applied before the heaters are on
2. What is the effect on every other part of the circuit if B+ arrives before anything is drawing load

Once you know the answer to those question, you have a handle on the problem you may have to solve.

If you do need to delay B+, then there are other options, a time delay relay for example.

Sorry, but I am going to have to get that t-shirt printed :-).
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
simon
Thermionic Monk Status
Posts: 5600
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

#13

Post by simon »

Nick wrote:Sorry, but I am going to have to get that t-shirt printed :-).
Will they be available in a choice of colours? :lol: I'll take one in blue please.
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#14

Post by pre65 »

Hi-what i have done is to put a switch in the 5V transformer mains feed.

I had a couple of spare switches and a place to insert them,so now i can use

my 5U3C.

Thanks for your advice Nick.
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
Post Reply