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A place to discuss member's DIY audio projects & post pictures/schematics. NOTE: There is a limit of 2MB per attachment, and a maximum of 3 attachments per message. If you need to post more than 3 attachments, just add another message.
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Re: Direct coupled screen drive amp...

December 24th, 2020, 9:18 pm

The primary winding on the output transformer isn't connected correctly.
Take a look at the original circuit on page 1.

ratbagp wrote:Roscoe, could you check this out? I can play with R4 as you suggest.

Image

Playing with PSUD I think I can get pretty close to 400 vdc.

ray

Re: Direct coupled screen drive amp...

December 24th, 2020, 10:57 pm

OK thanks.

Just finished the first bottle of champers!

ray

Re: Direct coupled screen drive amp...

December 25th, 2020, 6:12 am

Don't drink and screen drive...... :obscene-drinkingcheers:

ratbagp wrote:OK thanks.

Just finished the first bottle of champers!

ray

Re: Direct coupled screen drive amp...

January 6th, 2021, 6:57 pm

Our boxes have finally arrived. Now to start building after I find the appropriate parts after unpacking. I never realized how much I missed building until all my parts were packed away.

http://ratbagp.blogspot.com/2021/01/our-boxes-arrive.html

ray

Re: Direct coupled screen drive amp...

January 6th, 2021, 8:32 pm

I still have some of mine to unpack so I feel your pain. I've started pulling the wires from my audio room to the basement where my equipment rack is located.

Re: Direct coupled screen drive amp...

January 6th, 2021, 11:38 pm

ratbagp wrote:Our boxes have finally arrived. Now to start building after I find the appropriate parts after unpacking. I never realized how much I missed building until all my parts were packed away.

http://ratbagp.blogspot.com/2021/01/our-boxes-arrive.html

ray

And my wife wonders why I would never move. I moved to where I am now 29 years ago from my first house. I look at your pictures and it reminds me of the massive task it takes to relocate one's existence. :shock:

Re: Direct coupled screen drive amp...

January 7th, 2021, 1:23 am

Some 25 years ago when I started to get interested in building amps, I bought two of these cupboards from Ikea to store parts.

Image

My wife lusted after them and when she went to Ikea to get more they had disappeared, never to return. That lust has continued ever since and as part of the move, I have given them to her. She loves the little drawers.

Getting back to Roscoe's amp, in the course of unpacking some of the boxes I have come across the major parts I will need to build so I should be able to get cracking in the next few days.

ray

Re: Direct coupled screen drive amp...

January 7th, 2021, 11:07 am

ratbagp wrote:Some 25 years ago when I started to get interested in building amps, I bought two of these cupboards from Ikea to store parts.

Image

My wife lusted after them and when she went to Ikea to get more they had disappeared, never to return. That lust has continued ever since and as part of the move, I have given them to her. She loves the little drawers.

Getting back to Roscoe's amp, in the course of unpacking some of the boxes I have come across the major parts I will need to build so I should be able to get cracking in the next few days.

ray

That's a cool cabinet! My wife is into jewelry making and that piece would be perfect. What a shame they stopped selling them.

Re: Direct coupled screen drive amp...

January 14th, 2021, 7:51 pm

It's time to start building my version of the Roscoe.

Starting at the power supply, I have an Antek toroid 4TK400A. I plan to wire the primaries in series for the 240 vac here in Oz. I will have a thermistor on the primary.

https://www.antekinc.com/content/AN-4TK400.pdf

I've been playing with PSUD and I can get to about 430 vdc with tube rectification with a simple CLC of 10 uf DC Link, Hammond 193L (5H 300 ma 57 ohms) and 150 uf of DC link. I should be able to play with the input capacitor to lower or raise the final voltage.

I can use either 5AR4 or a couple of 6D22S. Which would you recommend out of the two? I have room for either case in my layout.

ray
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