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It is currently 20 Nov 2019, 18:30

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PostPosted: 20 Jul 2019, 13:14 
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Mains completed.

I used PVC cable (standard mains) and used heat shrink just on the ends of each joint to stop it melting away from the core.
:sleep:
Its the first time both Transformers have run up in correct positions, its under no load yet but it seems to be mechanically silent.
Next step is the 6x4 socket and remote wiring. Yawn.
I have secured the terminals on the tag board with JB weld on the inrush suppressor joints. (not in the pic)

Regards
M. Gregg


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PostPosted: 22 Jul 2019, 16:57 
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Input board fitted,

Wired with silver solid core for ground, and stranded silver for input wiring.

Regards
M. Gregg


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PostPosted: 23 Jul 2019, 12:27 
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6X4 rectifier wired,

Mylar insulation fitted behind the B+ fuse holder.
All ty-raps replaced.
I might fit a polyswitch fuse in line with the rectifier heater:
https://www.google.co.uk/search?q=polys ... z5fFGTsa1M:

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PostPosted: 26 Jul 2019, 15:44 
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Just doing some redesign,

I'm looking at LM317T wrap around and have modified the soft start board to allow this as an option.
Its a simple mod just allowing the insertion of a resistor in series with the input of the LM317 the other connections are already available.
So its just a new terminal block marked B/E (base and emitter of a PNP transistor).
Interesting links:
https://www.youtube.com/watch?v=yRRHqO5HDxA
http://www.bowdenshobbycircuits.info/page12.htm

If its not used then B/E are linked out.

Regards
M. Gregg


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PostPosted: 26 Jul 2019, 17:00 
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I would only have up to 3 days patitence (30Hours) of assembiling a amp and installing the parts inside.


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PostPosted: 27 Jul 2019, 02:28 
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ILoveHiFi wrote:
I would only have up to 3 days patitence (30Hours) of assembiling a amp and installing the parts inside.


I just enjoy the build, its interesting to try ideas and see the way around problems.
I'm just looking at the 5687 board and making it out of PTFE, so I find this interesting as well. :D Just fitted the lugs on the valve bases aka Kondo to fit the wire to retain the tubes..LOL
Its also a first try at making the nuts for the acrylic sides captive sticking them on the aluminium angle on one side of the nut with JB weld.

It was done last night so I'm going to remove the pins and see if the JB weld just snaps off.. :D
Its just for fun. If it works I'll do the bottom 4 nuts as well, its just easier for access.

Regards
M. Gregg


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PostPosted: 27 Jul 2019, 18:40 
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I would have troubble sleeping thinking of things if a build takes more than 3 days.
And in daytime I would think about it and thats the main reason why I wouldn't have much patence.

Not trying to show off, but for deminishing returns, the detail spent in installing the case.
Is more constructive in doing R&D with the same time.

I also noticed you have the added mass on the volume control linkage, to make the control feel very sexy.
Insaine attention to quality, good on you.


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PostPosted: 28 Jul 2019, 15:06 
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I have completed and fitted the LM317 wrap around.

I decided to fit it in the vent to drive the ventilation with the warmth of the pass transistor.
So I built a module see pic.
The values as shown in the previous links worked well so I used a BD912 transistor and a high wattage 10 Ohm resistor.
The resistor dosen't need to be high wattage but its just in case the pass transistor goes open to carry the current before the LM317 goes into auto shut down.

The wrap around works well and follows the voltage ramp, I tried it driving the two 5687 triode heaters which run at 12.6V at 1.05A continuous.
I will do a quick sketch to show the circuit and post it for anyone that might be interested.


Regards
M. Gregg


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PostPosted: 28 Jul 2019, 15:43 
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Here is,

the quick sketch of the circuit for the soft start voltage ramp with wrap around current boost.
It also shows a previous mod with the 1n4148 ramp transistor junction protection.
AB on the drawing is Ammo Bead suppression.

Regards
M. Gregg


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PostPosted: 02 Aug 2019, 12:42 
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I have been looking at,

PWM to replace the lm317 motor regulator (using some kite board)
I found a couple of MOD grade 555 timer chip in my parts box and looked at creating a direct replacement board.
I have a BUZ11 spare so I thought I would give it a try.

I have some testing to do but this is the result so far. I decided to use a terminal block to mount the BUZ11 so it can be easily replaced if required.
NB for anyone not familiar with MOD grade parts from the late 70's early 80's its a ceramic package with a ceramic seal. (look at the 555 in the picture)


Regards
M. Gregg


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