18 Watt Lite Test Readings?

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tatter75
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Re: 18 Watt Lite Test Readings?

Post by tatter75 »

That's a great idea. I know Weber do a WCA4 Copper Cap drop in replacement for an EZ81 but I can't seem to find them in the UK, would have to import it.

I'm not sure I have anywhere to mount the diodes within the chassis if I do it DIY.

I've seen a few diagrams using 4 x 1N4007 diodes and a 100ohm 10W resistor that seem simple enough, it's just how to situate them in the chassis. I'm assuming these parts will create a bit of heat and can't be near any wiring.
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Re: 18 Watt Lite Test Readings?

Post by JMPGuitars »

The 10W sag resistor is optional. I don't usually bother, but you can if you want. A good PT will give some tasty sag anyway.

Use UF4007 diodes; 1N4007 are slower/noisier. Personally, I often go straight from the secondary taps on the PT to the standby switch with the 4 diodes.

The Weber can thing is silly, and there's no point in it. Just use diodes if you're going to go SS.
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Re: 18 Watt Lite Test Readings?

Post by tatter75 »

As in mount the diodes on the switch?

Do you have any photos of how you do that?
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Re: 18 Watt Lite Test Readings?

Post by JMPGuitars »

tatter75 wrote:
Mon 05/13/24 12:26 pm
As in mount the diodes on the switch?

Do you have any photos of how you do that?
viewtopic.php?p=253674#p253674

viewtopic.php?p=253679#p253679
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Re: 18 Watt Lite Test Readings?

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That’s great! Thanks so much. I’ll order the parts and let you know how I go on.
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Re: 18 Watt Lite Test Readings?

Post by tatter75 »

I’ve finally got my Solid State Rectifier wired in. Sounds great, I opted to go for the 100 ohm resistor as well.

The DC voltage at the first filter cap is now 385v. I should be aiming for 345v so I plan to add two 20v 5watt 1N5357 Zener Diodes in series with the 2k2 resistor in between the first two filter caps next.

Also I’ve added shielded cabling to the inputs and that seems to have fixed my issue with the tone pot.
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Re: 18 Watt Lite Test Readings?

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tatter75 wrote:
Wed 05/22/24 11:02 am
I’ve finally got my Solid State Rectifier wired in. Sounds great, I opted to go for the 100 ohm resistor as well.

The DC voltage at the first filter cap is now 385v. I should be aiming for 345v so I plan to add two 20v 5watt 1N5357 Zener Diodes in series with the 2k2 resistor in between the first two filter caps next.

Also I’ve added shielded cabling to the inputs and that seems to have fixed my issue with the tone pot.
In my experience that sag resistor is completely obsolete. I wouldn't implement it the way you did either. It's a fairly heavy resistor and the wires can break off pretty easy. I remember this ruined my 1st Hammond PT. Maybe you can find out the significance for yourself. Just clip an on/off switch between the 2 wires using alligator clips. Don't forget to be safe when doing this. I use a thin wooden board to fixate the switch or pot when experimenting stuff this way. This prevents you for touching hot wires when you're doing the testing with a guitar on your lap.
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Re: 18 Watt Lite Test Readings?

Post by tatter75 »

Thanks, I may just clip the resistor off once I've got the voltage dropping diodes in place. It is a bit chunky! I've put heatshrink round the resistor legs and it feels fairly secure but I get what you mean. I had one of these break off in another amp I own once, so I'm aware it can happen.
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Re: 18 Watt Lite Test Readings?

Post by tatter75 »

Added a zener diode (only needed one in the end) and now my voltage in between the first two filter caps is bang on 345v.

Unfortunately my replacement pilot light blew after a few seconds, it was rated for 230v so that is a bit confusing. I have a replacement but it requires a larger hole in the chassis.
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Re: 18 Watt Lite Test Readings?

Post by Bieworm »

tatter75 wrote:
Thu 05/23/24 11:37 am
Added a zener diode (only needed one in the end) and now my voltage in between the first two filter caps is bang on 345v.

Unfortunately my replacement pilot light blew after a few seconds, it was rated for 230v so that is a bit confusing. I have a replacement but it requires a larger hole in the chassis.
Useful knowledge about the zener. But a single 5W zener will likely have to dissipate more heat than it can handle. It’s better to have more lower voltage 5W zeners in series so the heat dissipation will be spread over the multiple zeners.
About the pilot lamp… how is it wired in exactly? What’s the voltage on it?
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Re: 18 Watt Lite Test Readings?

Post by tatter75 »

The led was 230v red wire to live black wire to ground. The PT was reading about 235v so I’m assuming that’s why it blew?
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Re: 18 Watt Lite Test Readings?

Post by Bieworm »

tatter75 wrote:
Thu 05/23/24 3:30 pm
The led was 230v red wire to live black wire to ground. The PT was reading about 235v so I’m assuming that’s why it blew?
Naaah… I think you need to connect the black wire to the neutral terminal of the power transformer, not to ground. The lamp needs to be parallel with the 230/240V terminal and the 0V terminal
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Re: 18 Watt Lite Test Readings?

Post by tatter75 »

Sorry, that’s what I meant, not ground.
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Re: 18 Watt Lite Test Readings?

Post by JMPGuitars »

If you're still having trouble, share some photos of the LED and power switch wiring, including images of the PT.
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Re: 18 Watt Lite Test Readings?

Post by tatter75 »

Unfortunately I've already disconnected it but I'm using this wiring. I'm certain that I've wired the LED and the transformer correctly. I'll try to add some photos.

From the measurements I've made sometimes the mains supply is around 230v but sometimes it's 245v and above. It fluctuates.

It seems odd to me that the diagram I have is using a 240v lamp basically wired to the mains, whereas most diagrams I've seen use a 7v lamp wired to the filament wires.

EDIT: I bought an LED but the diagram calls for a 240v NEON. DOH!
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Re: 18 Watt Lite Test Readings?

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Bieworm wrote:
Thu 05/23/24 12:47 pm
Useful knowledge about the zener. But a single 5W zener will likely have to dissipate more heat than it can handle. It’s better to have more lower voltage 5W zeners in series so the heat dissipation will be spread over the multiple zeners.
About the pilot lamp… how is it wired in exactly? What’s the voltage on it?
Really? This is a worry then. The fluctuation in the mains here means that now my voltage in-between the first 2 filter caps is between 345vdc and 360vdc. So if I add a 5watt 5volt zener diode in series that should get me around the right voltage and hopefully help with heat dissipation?
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Re: 18 Watt Lite Test Readings?

Post by JMPGuitars »

Neon or LED bulb doesn't matter as long as they're the right voltage / type. If the bulb is rated for 230, and 240 is out of it's safe range, then it will die.

You can run a 6.3V lamp off the filaments instead, that's what I do. It's probably safer too. That diagram is a guide, not the law. However, you need to make sure your PT can handle the current draw of the tube filaments + lamp.
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Re: 18 Watt Lite Test Readings?

Post by Bieworm »

While I’m with Josh on using the filament voltage and a 6.3V pilot lamp… there’s also the option to drop the voltage to the pilot light by putting a resistor in series. For that you need to get the good ol’ Ohms law from the shelf😎
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Re: 18 Watt Lite Test Readings?

Post by tatter75 »

Bieworm wrote:
Fri 05/24/24 8:25 am
While I’m with Josh on using the filament voltage and a 6.3V pilot lamp… there’s also the option to drop the voltage to the pilot light by putting a resistor in series. For that you need to get the good ol’ Ohms law from the shelf😎
Is this relevant? I'm a complete newb so I have no idea what the maintain voltage or current draw of a neon is and if it's different from part to part.

https://www.anglia.com/newsarchive/pdfs/309.pdf
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Re: 18 Watt Lite Test Readings?

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JMPGuitars wrote:
Fri 05/24/24 8:14 am
Neon or LED bulb doesn't matter as long as they're the right voltage / type. If the bulb is rated for 230, and 240 is out of it's safe range, then it will die.

You can run a 6.3V lamp off the filaments instead, that's what I do. It's probably safer too. That diagram is a guide, not the law. However, you need to make sure your PT can handle the current draw of the tube filaments + lamp.
The highest rated neons and leds I can find are 240v, but my mains is fluctuating and going over 245v quite often so I think I would need a resistor if I use the mains supply.

If I want to use the filament supply from the PT how would I work out if it's possible?

I have very little info on the PT and the Neon except that it is rated for 240v. Can I measure this beforehand or do I just try it and see what happens?
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