Remember These?

What people are working on at the moment
Cressy Snr
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#481 Re: Remember These?

Post by Cressy Snr »

We have heaters on the power tubes. :)
Image

I'm using a smaller 25V transformer for the 13E1 heaters than I did on the breadboard. Heaters are running at 25.7V rather than the 27.2V of the breadboard version. This is far better; only 0.3V low instead of 1.2V high. Should give the valves an easier time.

That's all for today. The epoxy thermal bonding paste, holding the CCS chips to the underside of the top plate, needs to cure thoroughly before I do anything else with the amp. Providing nothing blows up, the OTL should, I would think, be running by Sunday at the latest.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
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Ray P
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#482 Re: Remember These?

Post by Ray P »

Cressy Snr wrote: Thu Mar 21, 2019 4:00 pm Yes, at the moment.
I'll be watching how the 13E1 works out with them...
Sorry, I couldn't resist!
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Ray P
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#483 Re: Remember These?

Post by Ray P »

Cressy Snr wrote: Thu Mar 21, 2019 4:48 pm That's all for today.
Coming together nicely
Sorry, I couldn't resist!
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Mike H
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#484 Re: Remember These?

Post by Mike H »

Image

Lurking.
 
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
Cressy Snr
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#485 Re: Remember These?

Post by Cressy Snr »

Been working on the thing all morning as an ultimatum has been given, that it is finished today. The missus is sick to death of the mess, that has been on the kitchen table for the last few weeks. So it's finish or bust!

Tea break over, back on yer 'eads.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
Ant
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#486 Re: Remember These?

Post by Ant »

Don't blow it up by rushing, tell Mi mam to nanas

Or tidy up so she isn't so annoyed :mrgreen:
Also starring Rex Hamilton as Abraham Lincoln

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Cressy Snr
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#487 Re: Remember These?

Post by Cressy Snr »

There's no chance of any rushing. It is doable.
Power supply is up and running at the correct voltage.
Next on the list are the power tube cathode arrangements and output caps. After that, the input driver boards only need mounting and plumbing into the PSU and volume control wipers as they are already populated.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
Cressy Snr
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#488 Re: Remember These?

Post by Cressy Snr »

Managed to get it finished by tea-time. I've had the heaters going on the output valves and the small signal stages, but there's absolutely no way I'm switching on the HT tonight.
Tomorrow, I go through it with a fine tooth comb, making sure the driver PCBs are connected to the right places on the power supply, that the feedback is not crossed between channels and that the output stage is done right. If I pop those fooking CCS chips, it is going to be a complete bastard to fit new ones. This thing is so tightly packed, I'm hoping against hope that it won't end up being a long wave radio transmitter.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
Cressy Snr
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#489 Re: Remember These?

Post by Cressy Snr »

Well, you all knew I wouldn't be able to resist :lol:
Image

I threw caution to the wind and just connected it up, let the heaters warm through for five minutes then threw the HT switch with a long stick.

It lives! It plays! There is no hum! Wahay! :mrgreen:
Sgt. Baker started talkin’ with a Bullhorn in his hand.
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Ray P
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#490 Re: Remember These?

Post by Ray P »

Great stuff Steve!

Has it retained the magic of your breadboard build?
Sorry, I couldn't resist!
Cressy Snr
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#491 Re: Remember These?

Post by Cressy Snr »

Ray P wrote: Sat Mar 23, 2019 7:06 am Great stuff Steve!

Has it retained the magic of your breadboard build?
Yep, it's as good as the breadboard. I decided to go pure point to point away from the PCBs and as a result, the wiring is 'Rozenblit neat' However, this has resulted in the quietest amp I've ever built.
Just a couple of things to put right:
I bought two values of feedback resistor and used the smaller value. Sod's law dictated that it would be the wrong one :lol:
The sound is beautifully pure but a bit 'tight, as a result.
Also I did my usual trick of reversing the channels at the input end. :roll:
Once these two minor issues are sorted, I'll report back.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
steve s
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#492 Re: Remember These?

Post by steve s »

Good news Steve.. glad it's going well
The tube manual is quite like a telephone book. The number of it perfect. It is useful to make it possible to speak with a girl. But we can't see her beautiful face from the telephone number
Cressy Snr
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#493 Re: Remember These?

Post by Cressy Snr »

Cheers Steve,

After having made the corrections to the feedback resistors and channel reversal, the amp is now properly installed in the system and making glorious music. I'm a happy chappy. :)
Image

Just need to make the transformer cover, but that can wait a couple of days. For now, I have a mammoth task to contend with, ie making the kitchen table at least presentable after my solder slinging sessions.
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Ray P
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#494 Re: Remember These?

Post by Ray P »

Excellent result Steve, it looks absolutely at home.

What are you planning with respect to the transformer cover - I imagine something creative to fit in with the retro look.

What feedback resistor did you settle on for your 16ohm load? It's probably about the value I should be aiming for.
Sorry, I couldn't resist!
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izzy wizzy
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#495 Re: Remember These?

Post by izzy wizzy »

I enjoy watching your process. Great result and well done.

Cheers,
Stephen
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