Low heater voltage- how raise it up higher?

18watt-specific Tech Talk - Building, Fixing, Parts, Mods...

Moderators: CurtissRobin, colossal, zaphod_phil, Daviedawg, Graydon

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 163
Joined: Mon 02/10/20 8:24 am

Re: Low heater voltage- how raise it up higher?

Post by Bieworm »

I fixed the wire to standby switch directly on pin 3 of the rectifier socket. So switch is no longer part of the circuit
Will the diodes make a difference? I mean connecting the 290V wires directly to the rectifier socket without the diodes in series ?

Edit: Tested without diodes.. no difference
1 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 163
Joined: Mon 02/10/20 8:24 am

Re: Low heater voltage- how raise it up higher?

Post by Bieworm »

I'm leaving it like this. The amp sounds incredible. Maybe less gain, yes. But I don't mind. I like the way it sounds.
And the drive monster is on its way anyway.. the JMP tremolo TMB ;)
0 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 1650
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Low heater voltage- how raise it up higher?

Post by JMPGuitars »

Just out of curiosity, what's your rectifier heater voltage with and without the rectifier tube?
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 163
Joined: Mon 02/10/20 8:24 am

Re: Low heater voltage- how raise it up higher?

Post by Bieworm »

JMPGuitars wrote:
Tue 03/24/20 2:18 pm
Just out of curiosity, what's your rectifier heater voltage with and without the rectifier tube?
5.9V without it
5.8V with it

Maybe things would be better when I wire the primary for 230V instead of 240V. The wall voltage today is 233V
1 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 1650
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Low heater voltage- how raise it up higher?

Post by JMPGuitars »

Bieworm wrote:
Tue 03/24/20 2:32 pm
Maybe things would be better when I wire the primary for 230V instead of 240V. The wall voltage today is 233V
Interesting. That could be the culprit. Let us know what happens.
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 163
Joined: Mon 02/10/20 8:24 am

Re: Low heater voltage- how raise it up higher?

Post by Bieworm »

JMPGuitars wrote:
Tue 03/24/20 2:38 pm
Bieworm wrote:
Tue 03/24/20 2:32 pm
Maybe things would be better when I wire the primary for 230V instead of 240V. The wall voltage today is 233V
Interesting. That could be the culprit. Let us know what happens.
Ok. 230V wiring performed. Heaters up to 5.9V across the heaters, but all values went up. The PT is rated for 300-0-300 HT.
Now the B+ is way up.
What do you suggest? Start tweaking the cathode bias resistor or wire the PT back to 240V ? Or put a resistor between the EZ81 and the first filter cap?
Second line of measurements is 230V , first line is 240V
15851510229358050200317521106758.jpg
You do not have the required permissions to view the files attached to this post.
1 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 163
Joined: Mon 02/10/20 8:24 am

Re: Low heater voltage- how raise it up higher?

Post by Bieworm »

Anyone?
0 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 1650
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Low heater voltage- how raise it up higher?

Post by JMPGuitars »

Well, 303 is a lot closer to the 300 spec than 289 is. That tells me that's where the PT is probably supposed to be. OTOH, 18W transformers are usually spec'd at 290-0-290 (some as low as 275-0-275) which is probably why your voltages are better the other way.

My suggestion is that since the variance in heater voltage isn't that significant, switch it back unless somebody smarter tells you not to. ;)

For the next build, try a different manufacturer for the PT. This one doesn't seem to suit the circuit too well.
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 163
Joined: Mon 02/10/20 8:24 am

Re: Low heater voltage- how raise it up higher?

Post by Bieworm »

JMPGuitars wrote:
Thu 03/26/20 6:29 am
Well, 303 is a lot closer to the 300 spec than 289 is. That tells me that's where the PT is probably supposed to be. OTOH, 18W transformers are usually spec'd at 290-0-290 (some as low as 275-0-275) which is probably why your voltages are better the other way.

My suggestion is that since the variance in heater voltage isn't that significant, switch it back unless somebody smarter tells you not to. ;)

For the next build, try a different manufacturer for the PT. This one doesn't seem to suit the circuit too well.
Too late. The parts for the TMB tremolo arrived yesterday and it contains the same 300V HT windings, except this one has only got the 230V option. The secondaries seem better OTOH on 230V.
So how about zenering the 300V's to 290V or add resistors between the 300V taps and the rectifier?

Also noticed that you use a 500K linear vol pot while the Standard TMB values a 500K log pot. Having a log pot in my classic has always made me wonder why it's log. It's nearly an on-off switch like this. If you want to play quiet with the log pot you need to tweak between zero and 0.5. Linear makes more sense
1 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 1650
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Low heater voltage- how raise it up higher?

Post by JMPGuitars »

Bieworm wrote:
Thu 03/26/20 6:45 am
Too late. The parts for the TMB tremolo arrived yesterday and it contains the same 300V HT windings, except this one has only got the 230V option. The secondaries seem better OTOH on 230V.
So how about zenering the 300V's to 290V or add resistors between the 300V taps and the rectifier?

Also noticed that you use a 500K linear vol pot while the Standard TMB values a 500K log pot. Having a log pot in my classic has always made me wonder why it's log. It's nearly an on-off switch like this. If you want to play quiet with the log pot you need to tweak between zero and 0.5. Linear makes more sense
Oh well, I guess you'll see how the new one reads. You can certainly use whatever safe method you want to drop the B+ and adjust the power tube cathode voltage to 12VDC.

I didn't use a linear volume. A500K is what it says. That's audio or log. B500K would be linear, and C500K would be reverse audio/log. Make sure you're paying attention to the schematic, there are linear pots in there for a few of the others.

Thanks,
Josh
1 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 163
Joined: Mon 02/10/20 8:24 am

Re: Low heater voltage- how raise it up higher?

Post by Bieworm »

JMPGuitars wrote:
Thu 03/26/20 7:12 am
Bieworm wrote:
Thu 03/26/20 6:45 am
Too late. The parts for the TMB tremolo arrived yesterday and it contains the same 300V HT windings, except this one has only got the 230V option. The secondaries seem better OTOH on 230V.
So how about zenering the 300V's to 290V or add resistors between the 300V taps and the rectifier?

Also noticed that you use a 500K linear vol pot while the Standard TMB values a 500K log pot. Having a log pot in my classic has always made me wonder why it's log. It's nearly an on-off switch like this. If you want to play quiet with the log pot you need to tweak between zero and 0.5. Linear makes more sense
Oh well, I guess you'll see how the new one reads. You can certainly use whatever safe method you want to drop the B+ and adjust the power tube cathode voltage to 12VDC.

I didn't use a linear volume. A500K is what it says. That's audio or log. B500K would be linear, and C500K would be reverse audio/log. Make sure you're paying attention to the schematic, there are linear pots in there for a few of the others.

Thanks,
Josh
Ok. I think I'll start with a 150R resistor instead of a 100R on the rectifier on the TMB tremolo design.
Sidenote : I find it really hard to wire the heaters. 2 wires combined are a little too thick for the holes in the lugs. I put 1 wire through and twist the other around the one.
0 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 1650
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Low heater voltage- how raise it up higher?

Post by JMPGuitars »

Bieworm wrote:
Fri 03/27/20 12:15 pm
Ok. I think I'll start with a 150R resistor instead of a 100R on the rectifier on the TMB tremolo design.
Sidenote : I find it really hard to wire the heaters. 2 wires combined are a little too thick for the holes in the lugs. I put 1 wire through and twist the other around the one.
Stop it. That's no good. What gauge wire are you using for the heaters? What brand/type of sockets?
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 163
Joined: Mon 02/10/20 8:24 am

Re: Low heater voltage- how raise it up higher?

Post by Bieworm »

JMPGuitars wrote:
Fri 03/27/20 6:01 pm
Bieworm wrote:
Fri 03/27/20 12:15 pm
Ok. I think I'll start with a 150R resistor instead of a 100R on the rectifier on the TMB tremolo design.
Sidenote : I find it really hard to wire the heaters. 2 wires combined are a little too thick for the holes in the lugs. I put 1 wire through and twist the other around the one.
Stop it. That's no good. What gauge wire are you using for the heaters? What brand/type of sockets?
Don't know the brand. No beltons , but ceramic sockets. The holes are smaller. Same sockets as the previous build and same wire.. 18 gauge.
Don't worry, their pretty fixed and in the same solder
You do not have the required permissions to view the files attached to this post.
0 x
"THIS should be played at high volume..preferably in a residential area"

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 1650
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Low heater voltage- how raise it up higher?

Post by JMPGuitars »

Bieworm wrote:
Fri 03/27/20 6:09 pm
Don't know the brand. No beltons , but ceramic sockets. The holes are smaller. Same sockets as the previous build and same wire.. 18 gauge.
Don't worry, their pretty fixed and in the same solder
You don't need 18AWG. I usually use 20AWG pre-tinned/bonded wire. Marshall usually uses 22AWG. This is why you have trouble with the heaters.

I ONLY use 18AWG wire for speakers, and the Mains connections including the power switch, and PT connections to the mains. Everything else is 20AWG. I would use 22AWG too if I ever find a brand I like.

With those sockets I would use 22AWG. I don't bother with ceramic. Ceramic can be really good or really bad, and also can be inconsistent. I have no issues with consistency or quality with the Beltons.

Thanks,
Josh
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale

User avatar
Bieworm
Occasional poster
Occasional poster
Posts: 163
Joined: Mon 02/10/20 8:24 am

Re: Low heater voltage- how raise it up higher?

Post by Bieworm »

JMPGuitars wrote:
Fri 03/27/20 6:32 pm
Bieworm wrote:
Fri 03/27/20 6:09 pm
Don't know the brand. No beltons , but ceramic sockets. The holes are smaller. Same sockets as the previous build and same wire.. 18 gauge.
Don't worry, their pretty fixed and in the same solder
I looked it up. Tis 1mm2 wire, so that's .78mm diameter ...that corresponds with 20AWG
You don't need 18AWG. I usually use 20AWG pre-tinned/bonded wire. Marshall usually uses 22AWG. This is why you have trouble with the heaters.

I ONLY use 18AWG wire for speakers, and the Mains connections including the power switch, and PT connections to the mains. Everything else is 20AWG. I would use 22AWG too if I ever find a brand I like.

With those sockets I would use 22AWG. I don't bother with ceramic. Ceramic can be really good or really bad, and also can be inconsistent. I have no issues with consistency or quality with the Beltons.

Thanks,
Josh
I thought it had to be that wire. They sold it on the first build kit as to use wire.
Shoot!!!
I'll give it a shot like this. If there are problems I will change that. And in the meantime I will order 20 guage just in case.
Last edited by Bieworm on Sat 03/28/20 4:39 am, edited 1 time in total.
1 x
"THIS should be played at high volume..preferably in a residential area"

Post Reply