12xxx Larry Ground
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- clusterstudios
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Re: 12xxx Larry Ground
does anybody off hand know the drill bit size of the power tube screw holes??
Joseph
- vanhalen5150
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Re: 12xxx Larry Ground
5/32"clusterstudios wrote:does anybody off hand know the drill bit size of the power tube screw holes??
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Re: 12xxx Larry Ground
You are right. I initially had #5 close to the PT but when I mounted it with brackets the hole got in the way so I re-drilled a new one. Thank God I made it more than 1" away .vanhalen5150 wrote:If your using a PT bracket, your probably an 1" away already.
I didn't have 5/32 so I used 3/16. A little loose but still fits nicely
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Re: 12xxx Larry Ground
Hi.
Do you guys ground the 1ohm resistors to the ground lug on each power tube (regular method) or do you send them to ground to another spot as per the JTM45 or JMP50 Larry's grounding scheme???
Thanks!
Do you guys ground the 1ohm resistors to the ground lug on each power tube (regular method) or do you send them to ground to another spot as per the JTM45 or JMP50 Larry's grounding scheme???
Thanks!
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Re: 12xxx Larry Ground
Yep, right to the socket bolt lug, just be extra careful that you are getting good metal contact with the lug for a secure ground. You can also just use a buss wire to ground and bias a different way, but the 1ohm resistor is the safest. I've seen dedicated ground bolts for the power sockets, which makes sense because there would be less chance of the lug coming loose from changing tubes over the years. Check out John Suhr's approach to this, pretty cool:
https://www.dropbox.com/s/5og36yddsy63bsi/SL68.jpg" onclick="window.open(this.href);return false;
https://www.dropbox.com/s/5og36yddsy63bsi/SL68.jpg" onclick="window.open(this.href);return false;
- vanhalen5150
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Re: 12xxx Larry Ground
I could never make out what exactly those things are he has in there? Anybody know?
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Re: 12xxx Larry Ground
They sort of look like the same "posts" or micro boards that the 68k input resistors are wired to by V1. You can see them a bit better at V4.
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Re: 12xxx Larry Ground
Hi there!
I've got a screen wire on my mains transformer (green/yellow). I know it needs to be grounded and have grounded it at spot #4. Is that right or does it need to be somewhere else? Her's the transformer data sheet:
http://www.ig-transformatoren.com/catal ... m100rs.pdf
Thanks!
I've got a screen wire on my mains transformer (green/yellow). I know it needs to be grounded and have grounded it at spot #4. Is that right or does it need to be somewhere else? Her's the transformer data sheet:
http://www.ig-transformatoren.com/catal ... m100rs.pdf
Thanks!
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Re: 12xxx Larry Ground
Yes, #4. Just a reminder: use medium bolts, a star washer against the inside of the chassis and at least two lugs per ground except #5. Allow a good length of wire so you can lift the board for access and future tinkering. Robert has a chassis shot somewhere here showing all the correct ground locations.
- vanhalen5150
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Re: 12xxx Larry Ground
I could be wrong but I think that yellow/green usually has to be extended and go all the way to #1. The screens/mains ground comes off the small cap board. Some trannys its 2 different colors. The new Merc I have is green/blue.
The yellow/green(edit: "on your diagram") is a tranny ground correct?
The yellow/green(edit: "on your diagram") is a tranny ground correct?
Last edited by vanhalen5150 on Wed Sep 25, 2013 8:15 am, edited 4 times in total.
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Re: 12xxx Larry Ground
Whoa! The screen wire he is talking about is a shield for the tranny itself. I would post this question in the Transformer forum before connecting it.
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- vanhalen5150
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Re: 12xxx Larry Ground
Yeah, from the diagram its from the tranny itself. So it would be #5?
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Re: 12xxx Larry Ground
OK, the number 16wire is odd, it's all kind of odd. What are the two brown wires (6 and 7)? Is wire #1 the common? wire 11 to ground #4 and wire 14 (Heater CT) to ground #1 Is wire 16 redundant (just ground it close to the PT)? I want to try a set of Ingo's tranny's now that he is back in business.
- vanhalen5150
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Re: 12xxx Larry Ground
Odd. 6 and 7 are listed(blue) as though they should be on the secondary side. 15V @1amp?
The way the two 120v and 240v scenarios are drawn out, #4 is the common ground on the primary for both voltages.
Is 16 just grounding the entire tranny?
The way the two 120v and 240v scenarios are drawn out, #4 is the common ground on the primary for both voltages.
Is 16 just grounding the entire tranny?
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Re: 12xxx Larry Ground
I wonder if it just insures a solid ground given that the lacquered laminates might prevent contact with the chassis in some cases, those Germans are pretty thorough, good beer too.