Weird Heater Supply Problem - And other solutions!

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marshallnoise
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Re: Weird Heater Supply Problem - 95VAC? WTF?

Post by marshallnoise » Mon Sep 18, 2017 7:52 pm

Rad! Will do!

I need to wait for some extra coupling caps to come in since after a few minutes I lose bias voltage. I am using some old mustard c 1970 400v caps in the amp that seem to have had it.

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Re: Weird Heater Supply Problem - And other solutions!

Post by Littlewyan » Tue Sep 19, 2017 7:41 am

Oh right, that's odd.

Where your bias circuit connects to the PT tap, what capacitor have you used?

On my standby switch I've put a resistor across it so there is some voltage in the amp when it's in standby but not enough to actually turn the amp on. Reason for this is it helps the Cathode Follower at start up.

marshallnoise
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Re: Weird Heater Supply Problem - And other solutions!

Post by marshallnoise » Tue Sep 19, 2017 10:44 am

Littlewyan wrote:
Tue Sep 19, 2017 7:41 am
Oh right, that's odd.

Where your bias circuit connects to the PT tap, what capacitor have you used?

On my standby switch I've put a resistor across it so there is some voltage in the amp when it's in standby but not enough to actually turn the amp on. Reason for this is it helps the Cathode Follower at start up.
The cap I am using its a 0.0047u 630v Yellow do-hickey. Its what I had on hand. I will get the proper one that Rob Robinette recommends later. I need quite a few items anyway from capacitor-land. Besides, I want to re-purpose that cap for the Soldano Depth Mod I like. Oddly, the amp has tons of low end already.

I will install that resistor you mentioned. I read it also prevents flyback voltages and other stupid stuff from going on.

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Re: Weird Heater Supply Problem - And other solutions!

Post by Littlewyan » Tue Sep 19, 2017 7:04 pm

Yes you need a Class X Capacitor I believe it's called. I can't remember off hand what one I used but I managed to find one with long enough legs to use on a turret board. I can find out the part number if you like.

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Re: Weird Heater Supply Problem - And other solutions!

Post by marshallnoise » Wed Sep 20, 2017 1:41 pm

Found it! And ordered it. Its a ceramic disc capacitor that is X1 and Y1 rated. Its an interesting thing. Its kind of expensive at $6.50 or so.

Capacitors 250V 0.05uF 20%
Vishay 125LS50-R
Mouser 75-125LS50-R

When the parts come in, I will wire up the standby the way described by Valvestorm. I am also going to play with the PI coupling cap value and change it to .082uf to see if I can take some of the girth out of the amp.

:clap:

Then I will post pics and you can mock me relentlessly. LMAO!

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Re: Weird Heater Supply Problem - And other solutions!

Post by marshallnoise » Thu Sep 21, 2017 2:23 pm

For those who are curious, I installed a new PI coupling cap and the red plating happened anyway. I swapped the pair of tubes to the other sockets and the red plating followed the tubes. Reading on the net told me that its possible that one of the tubes in that pair could have a grid leak and therefore draws more current than it should. Its possible that only one of the tubes is bad in the pair.

FYI, brand new from AES (yes, I have been reading that they aren't doing proper burn in times). :palm:

EDIT: Got to love their return policy though, they are sending me out a new quad when they receive the old quad.

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Re: Weird Heater Supply Problem - And other solutions!

Post by Littlewyan » Fri Sep 22, 2017 7:30 am

Yeah I think that one will do the job. I believe that's what I was going to buy originally but I couldn't find any at a decent price for me. Or they were out of stock. Can't remember!

Get the new quad in there then see what the low end is like. Have you got the amp completely stock? NFB as well?

The settings I use on mine are:

PV: 7
MV: 8.5
Bass: 5/6
Middle: 6.5
Treble: 5
Presence: 5 (sometimes 1 depending on the room)

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Re: Weird Heater Supply Problem - And other solutions!

Post by marshallnoise » Mon Sep 25, 2017 5:41 pm

I forgot to tell you a couple things. First, I am using the Ceriatone layout from 2013 less the loop and half power switch. And I am using 6L6s instead of EL34s. Completely stock less the bright cap and I do have the 100K NFB resistor in there. The amp is not very bright at all, which is super strange to me. But it could be the JJ preamp tubes I have in there or I have screwed up a value somewhere.

I did manage to get most of my issues resolved with a set of 5881s I had laying around. I have my depth mod wired in and it works great. I also rewired some of the amp because I was getting a lot of noise due to the chassis tube layout versus my board. Lots of long runs of wire, which sucks. I had to use a shielded wire for the middle lug of the master volume pot to the board (ground at pot) and the same for the presence pot. This has killed a lot of the ambient noise and hum I have.

Oh, and I moved the PI filter cap to the far side of the board near the power transformer because where I had it originally located, I was getting lots of noise.

The only thing I have now that is an issue is that the rectifier seems very noisy. I get an audible buzz from the area that translates through the amp on the high input with the treble anywhere above half. When I roll the treble back, the noise is greatly diminished. When I plug into the low input, the noise is gone. So I am going to look at the input jack wiring again and see if I have an issue there.

I also have the 0.22uf caps near the rectifier that are supposed to be snubbers I believe. I notice a lot of these amps' layouts have those removed. So I may do that too.

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Re: Weird Heater Supply Problem - And other solutions!

Post by Littlewyan » Tue Sep 26, 2017 3:28 am

No bright cap will be why it seems to have a lot of bass. Clip it in and try it.

Can you host some photos somewhere so I can take a look at your layout? We can try and make it quiet.

And what do you mean snubber caps? How are they wired? And what rectifier are you using?

And check that the presence works correctly in case you've got the NFB in phase rather than out of phase. Because of the low NFB on these amps it's quite subtle if you have it wrong.

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Re: Weird Heater Supply Problem - And other solutions!

Post by marshallnoise » Wed Sep 27, 2017 3:23 pm

Ok, commence the laughter!

ImageIMG_20170927_073640765 by Paul Abbott, on Flickr

ImageIMG_20170927_073730520 by Paul Abbott, on Flickr

ImageIMG_20170927_073646471 by Paul Abbott, on Flickr

ImageIMG_20170927_073650488 by Paul Abbott, on Flickr

ImageIMG_20170927_073654598 by Paul Abbott, on Flickr

ImageIMG_20170927_073706096 by Paul Abbott, on Flickr

ImageIMG_20170927_073720392 by Paul Abbott, on Flickr

ImageIMG_20170927_073723891 by Paul Abbott, on Flickr

:palm:

It is pretty clear that I need a different chassis for this type of amp. So this is a compromise for sure. I am probably going to buy a blank from somewhere and then drill my own holes and transplant this stuff in there.

The snubber caps I was referring to are to the left of the Full Wave Bridge Rectifier. Oh and the presence pot works fine.

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neikeel
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Re: Weird Heater Supply Problem - And other solutions!

Post by neikeel » Wed Sep 27, 2017 5:13 pm

Definitely has teh prototype look :wink:

I cannot see exactly how the snubbers are wired, typically across the rectifer HT and depending on the B+ at least 1000v rated.
If you use modern diodes you probably dont need them.

I agree a different chassis might help. How are you filter caps held in place?

The neatest chassis I have seen is te valvestorm one with undrilled front panel, I need to get one of these myself soon for another trem to AFD amp but have got bogged down in Orange plexi amps at the moment and my son has started building too.
Neil

marshallnoise
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Re: Weird Heater Supply Problem - And other solutions!

Post by marshallnoise » Wed Sep 27, 2017 5:20 pm

Hahahaha! That is about the kindest thing anyone could say about the wiring.

The snubbers are wired as you said. I am using modern 1000w 1n diodes so I figure they are fine.

How are the filter caps mounted? Hot glue. LMAO!

EDIT: I have some nice sheet metal on the side of my house, I am gonna make my own box this weekend. I have a welder too. :rock:

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Re: Weird Heater Supply Problem - And other solutions!

Post by marshallnoise » Thu Sep 28, 2017 12:37 am

https://youtu.be/gWHCGMK4QgM

And here is the noise I am fighting.

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Re: Weird Heater Supply Problem - And other solutions!

Post by Littlewyan » Thu Sep 28, 2017 7:41 pm

Ok push those tone stack wires down to the chassis and keep all wires as short as possible whilst still leaving them long to be pushed into quiet positions.

Also I can see that V1's anode wires are very close to the output section. Try moving them, see if the buzz changes. Poke around with a chop stick to see if you can make the buzz change.

Have you turned the amp on in another room? Definitely not something nearby causing the buzz?

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Re: Weird Heater Supply Problem - And other solutions!

Post by marshallnoise » Thu Sep 28, 2017 7:45 pm

I will move the wires around a bit and see if it improves.

I will also move the amp into another room and see if it makes a difference. There is a dimmer on the wall, but I do not believe its on the same circuit. I do think that when I get my chassis situation rectified, I will get some of this cured.

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