GroupDIY Bridge compressor.

[erikb1971]

How cool is that? Very Cool! Very DIY Dave!
Does this mean you can use any old meter as a dB meter as long as you change the scale thingie?

Erik

 

[DaveP]

Hi Erik,

You can for vari-mu types where the current reduces.

A 1mA fsd is fine with a bypass pot to zero it, maybe another resistor as well.

A real VU meter has a diode bridge, a 3.6k series resistor and special ballistic movement.

The meter cost me £3.70 from Ebay plus postage. lovely quality from the 1940's.

best
DaveP

 

[lassoharp]

I like the way you did the grounding busbar.  Were the middle supports just separate pieces cut to length and then soldered?


Meter looks fantastic.  Probably would take me a whole day!

 

[JayDubrek]

Looking at how neat your work is makes me feel quite ashamed of my own efforts! Lovely meter by the way....
Jay

 

[letterbeacon]

Lovely stuff Dave!

What do you use for the bus bar?  I'm about to put an order in at RS, I'm assuming it's something you got from there...?  What gauge is the hook up wire?

Thanks!

 

[DaveP]

Were the middle supports just separate pieces cut to length and then soldered?

That's it, just pre-bend them first, then pinch them on the busbar so you can solder them.

This is not my idea, most of the amps I used to dismantle in the 60's used that technique.  The US seems to go in more for separate turret boards, which lend themselves more to mass production techniques, I guess, one person building boards and another wiring them in.

best
DaveP

 

[DaveP]

What do you use for the bus bar?

RS 355-041

The hook up wire I've got in different colours in reels at work, its slightly too thick really but I'm too cheap to buy my own!  It's tinned which is most important, never buy untinned hook up wire, its almost impossible to solder when its tarnished after a while.
Typical part number is RS  356-690
best
DaveP

 

[lassoharp]

I've used a common metal clothes hanger before.  Just sand the finish off and rebend.  Fairly thick though.

 

[DaveP]

I've used a common metal clothes hanger before.  Just sand the finish off and rebend.  Fairly thick though.

Good idea but that would be iron, I think you would really need copper for the low resistance for a ground wouldn't you?.

I'm off to bed now, early start tomorrow.

all the best
Dave

 

[lassoharp]

I think mine were some type of steel or aluminum.  Probably not the best but it worked well enough.

 

[DaveP]

Busy weekend saw most of the components fitted, luckily there is plenty of room in the chassis to fit things neatly.  Heat sinks are ready to fit the  DC schottky rectifier, and Mosfet regulator.

It looks complicated but if you do the heater wiring first then methodically wire one tube at a time, marking a spare schematic as you go, its not as bad as it looks.

All the caps are labelled so EMRR can find his way around in 10 years time!
Pre-wiring the connections makes it easier to connect the back to the chassis later.

Tommorrow I will fit the back and fire up the tubes to check the DC voltage, remembering that the heaters are elevated to 43V

Don't let me forget to rewire it for 115V when it goes stateside!
Later this week I'll finish off the front panel wiring.
best
DaveP

 

[ruairioflaherty]

Outstanding Dave, loving the build.

 

[strangeandbouncy]

Such precise, neat wiring . . . . sigh . . .


    take note, Guys n' Gals!


  this is how it should be done!

 

[DaveP]

Such precise, neat wiring

Several people have said that, but I'm only doing my best to copy how it used to be done.  In fact I don't think I come up to the mark compared to what I've seen in the past.  I guess this method of electronic construction is just of historical interest now, but I promise you I will never do a SMA (Stupid Microscopic Artifacts) project.

rant over
best
DaveP

 

[alexc]

beats the sh*t out of my wiring   

 

[rafafredd]

Yes! Best PtoP ever!

 

[joe-electro]

I love the idea of using sawed off coffee cans for transformer screens. I'm going to have to steal that, if you don't mind.

Joe

 

[DaveP]

I love the idea of using sawed off coffee cans for transformer screens. I'm going to have to steal that, if you don't mind.

Joe

Enough to change brands to get the cans? ;D

Its French "Illy" coffee beans. :

DaveP

 

[DaveP]

Almost there now....

The back panel is finished and wired in.  Labelled screened cables will connect to the front panel.

The front panel has all its components in place, the dB meter is secured with brass screws and nuts to avoid magnetic interference.

From top left to right...Attack, Release, Threshold & Neon.

Bottom left to right...Comp in/out, Input level, Output level & Power on off.

The back of the front panel ready to wire.

All the pots are conductive plastic types for low noise.

I hope to finish it next week and test the specs.

best
DaveP

 

[DaveP]

Finished wiring in all the components tonight.

The front panel wiring

All the tubes in ready for lighting up.

I only put the fuse in for the heater supply to start with, everything worked ok but voltage was too high so turned off and added more resistance between the smoothing caps.  Turns out this supply needs 1.18 ohms, so will have to fit a 0.18 ohm plus the 1 ohm already there.  I'll have to drill 2 new holes but it can wait till tomorrow now....

Only job left to do is cut out and fit the top cover, that will be done lunchtime.

I'll fire up the HT with a fresh brain and quicker reactions tomorrow!

best
DaveP