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TSE & 45's

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awkwardbydesign

Member
Joined 2005
Are you going to fit everything to the top plate? Even so, I would suggest having the bottom removable might be a good idea. My type 26 has NO bottom, for ease of access, but I lined the sides with aly foil for screening. Others have used copper foil, but I had the aly!
BTW, what is the circuit for this amp? I have only seen this thread; I assume it is in another thread?
 
A

awkwardbydesign

Member
Joined 2005
BTW, if you are mounting Hammond chokes (which have a tendency to vibrate, I have been advised) to a metal plate, using these rubber mirror screw bushes can help isolate them. Available from your local glass merchant, probably. I find them very effective.
RUBBER_MIRROR_BUFFERS77310_thumb.jpg
 
E

evanc

Member
Joined 2009
mkane77g said:
7 hrs later and we have mucic. FM with a passive volume control. B+ is at 150v, B- 195v. Seems low. Should I change the value of C4? I'm tickled it's a music maker.
Click to expand...

Glad you got it running.

B+ and B- look reversed.... B+ looks low. Do you have a choke in place of r4? Increasing c4 will increase b+ voltage. Check the rectifier tube data sheet it will specify a maximum value for c4. I ended up with a very low value for c4 to get the b+ voltage in range.
 
mkane77g

mkane77g

Member
Joined 2014
Thanks. I'll get a few different flavors for C4. I have 4 Multimeters. I good digital and 3 cheap analogue and can't hardy figure out where to place the dial let alone read the meter. I'll get a couple more decent units. And My top plate arrives tomorrow.
 
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mkane77g

mkane77g

Member
Joined 2014
Yes, white and black. It is high. What can I do get it near 300v?
It's amazing how many mistakes one can make doing a build like this. I got the hole wrong for the rectifier tube so I ordered one of those socket savers hoping it fit's thru the hole. If I have to take a file to this I'll be a bit upset. I also put the hole for the fuse to close to the IEC plug so I now have to use one of those push in plugs. And I got the rabbet wrong in my base so I cannibalized a bit to make it fit. Planned on making another one from Walnut anyway. Taking a break.

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An externally hosted image should be here but it was not working when we last tested it.
 
W

w5jag

Member
Joined 2007
mkane77g said:
..... What can I do get it near 300v?
Click to expand...

There are different ways of lowering the B+.

That appears to be a 5U4 rectifier tube in your build. At your present experience level, a different rectifier tube is probably the right method.

You can realize a significant B+ reduction by replacing the 5U4 with a 5Y3 type (preferred) or 5W4 rectifier. Either can supply enough current for this amp with 45's.

If that is a 5R4 rectifier in your build, you will still realize some B+ reduction, but not as much.

Win W5JAG

edit: be advised the Sovtek 5Y3 is not a 5Y3, so avoid it. It is more like a fragile 5V4.
 
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