OK…so I’m on wi’ summat

[Cressy Snr]

Yes, as Phil said, it’ll only work harden if repeatedly bent backwards and forwards, then it’ll snap.

[Cressy Snr]

A bit of progress on the chassis today:

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[Cressy Snr]

The NVA based solid state amp is currently doing sterling service in place of the valve amp.

That’s the great thing about hi-fi; you always get 2 improvements. The first one came when I replaced the NVA based amp with the valve amp, the second, when I replaced the valve amp with the NVA based amp.

I’ll get yet another improvement when I put the rebuilt valve amp back in. I mean what’s not to like?

[Paul Barker]

That represents a lot of hard work not to be under estimated. But you and me both are coming back from darkness. In my case the project was decided on as a task. We’re both rising from the ashes.

I’m sat here listening to West Side Story. The amp is right way up. The task is complete.

Havent taken it up to the third floor where the Quad 57’s are yet. But I know it will shine on them. No heating up there though.

These Kef’s are quite good though, and this amp is now shining to full power with ease. Some of the 2nd juggling from the two out of phase stages is working out to reduce what 2h could have risen to. Something must have worked right. And the biggest difference to the power supply was the cap to b+. I was already super happy with the emp and its been supercharged by that last alteration. I even spoke of it not expectant. The rediculous part of that is the last power supply cap is Black Gate . A cheap Motor Start Cap has bettered a Black Gate! Somat like 26£ the pair.

Though Ive never found Black Gates better than Paper in Oil and Polypropylene in oil. Ive just lost confidence in old paper oil caps. That medium was one of the parts that failed me along the path. These modern caps are a better bet failure eyse. And two wound components have let me down on this journey out of darkness.

I’m not envious of you’re skills building neat insides to you’re amps, I am in awe of your skill. Its just not for me. All Im doing is puting a breadboard amp inside a shot to bits chassis. Which serves that purpose.

[Cressy Snr]

…We’re both rising from the ashes…

Definitely Paul.
It’s the making and the metalwork, planning the layout, dressing the leads inside, whilst trying to take care not to create unnecessary stray capacitance that I like. My head is only just starting to get around designing the circuits themselves again, but I’m getting there.

I spent a couple of hours today cutting and dressing the big holes for the three giant 80uF, 500VAC motor-run caps. It’s mindful and therapeutic; to me at least.

[Cressy Snr]

A little more progress:

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Caps, power transformer and choke mounted. Output transformers tomorrow.

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[Cressy Snr]

Inside so far:

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Brass bars held by M5 bolts keep the caps in place and rectifier socket hole has been punched.

[simon]

Good stuff Steve

[Cressy Snr]

Cheers Simon,

Output transformers are now mounted. Took me all day. Not as fast as I was, but it’s not about speed or urgency; not these days.

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Valve sockets will go in tomorrow along with the input sockets and speaker outlets. Rest of the infrastructure (tagstrips, busbar etc) on Thursday

[Cressy Snr]

Mains and heater wiring are in and tested:

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Had trouble with the primary 240V series connection. It's a long time since I used this particular Danbury mains transformer. I'd taken the labels off and lost the documentation. That was a good move wasn't it.
I'd identified each half with a multimeter, but was then stuck concerning the phasing of each half. I didn't want any fireworks or fuses blowing, so sat there scratching my head for half of yesterday, trying to find a solution to sort out the primary phasing without the use of a VARIAC.

This morning I used my signal generator set to 50Hz, in order to put a few volts onto the primary. Then on the secondary side I looked for an AC voltage with the multimeter. A voltage out on the secondary and we were in phase on the primary. No voltage out and we were out of phase and in blowing fuses or worse mode. I got it sorted.

Onwards...

[Cressy Snr]

Earthing system is in place plus the choke snubbers:

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And of course we have heaters:

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That's it for today.

[Paul Barker]

Envious

[Paul Barker]

Oh pooh, really sorry to have to tell you this, honest I wasn’t copying you. I adjusted b+ in my amp to get g2A 425v the bias on the cathode 39v 48 mA. 21 watts dissipation. Totally better by a mile than the 6550.Diana just nuck up on me, I nearly jumped out my skin. “Gosh its sounds really……significant.”

So its now a EL34 Triode amp.

Vade mecum says 2nd 8% power 6 watt. It has come alive. EL34 transes the 6550.

[Mike H]

Nice Steve. Does aluminium work-harden at all or can it be bent "in one"?

It does work harden so you probably have only the one chance to get it right. Steel is more forgiving but harder to get moving in the first place. Copper would be a brilliant option for bending.

My experience has been, alu can't be bent twice, on the same fold.

[Cressy Snr]

My experience has been, alu can't be bent twice, on the same fold.

Indeed!