DIY Transistor Amp Using NVA Boards
- Cressy Snr
- Amstrad Tower of Power
- Posts: 10582
- Joined: Wed May 30, 2007 12:25 am
- Location: South Yorks.
#76 Re: DIY Transistor Amp Using NVA Boards
The broken down Sony CD player has been gutted to give a nice, solid, heavy chassis for the next chapter in the evolution of the NVA clone. I don’t have to order anything for this project, just needed to do a bit of creative up-cycling of the CD player.
This new iteration of the NVA clone will have twin power supplies; one for the front end and the other for the driver/power stage. I’ve done a preliminary layout below: It’s quite a nice chassis, with partitioned off, screened sections. TBH, I’m not particularly enamoured with the layout above, but it does show the generous size of chassis available to work with.
Comments from the panel will be much appreciated.
This new iteration of the NVA clone will have twin power supplies; one for the front end and the other for the driver/power stage. I’ve done a preliminary layout below: It’s quite a nice chassis, with partitioned off, screened sections. TBH, I’m not particularly enamoured with the layout above, but it does show the generous size of chassis available to work with.
Comments from the panel will be much appreciated.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
- Cressy Snr
- Amstrad Tower of Power
- Posts: 10582
- Joined: Wed May 30, 2007 12:25 am
- Location: South Yorks.
#77 Re: DIY Transistor Amp Using NVA Boards
Better layout after removing one of the partitions:
Sgt. Baker started talkin’ with a Bullhorn in his hand.
- pre65
- Amstrad Tower of Power
- Posts: 21400
- Joined: Wed Aug 22, 2007 11:13 pm
- Location: North Essex/Suffolk border.
#78 Re: DIY Transistor Amp Using NVA Boards
Personally, I like the first layout better.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#79 Re: DIY Transistor Amp Using NVA Boards
Probably because you like symmetry more than keeping the transformers further away from the PCB's.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
- Cressy Snr
- Amstrad Tower of Power
- Posts: 10582
- Joined: Wed May 30, 2007 12:25 am
- Location: South Yorks.
#80 Re: DIY Transistor Amp Using NVA Boards
Aye, with the second layout, the transformers are as far away from the input stages as it’s possible to get them.
As soon as I’d done the symmetrical layout, I knew it was sub optimal, especially given the fact that there are two power supplies.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
- Cressy Snr
- Amstrad Tower of Power
- Posts: 10582
- Joined: Wed May 30, 2007 12:25 am
- Location: South Yorks.
#81 Re: DIY Transistor Amp Using NVA Boards
Made up a base from black painted 3mm aluminium sheet, plus a couple of angle brackets for the heatsinks:
How it looks in the chassis:
Power transistors temporarily mounted to check that positioning holes were drilled in the right places.How it looks in the chassis:
Sgt. Baker started talkin’ with a Bullhorn in his hand.
#82 Re: DIY Transistor Amp Using NVA Boards
I assume you will be isolating the transistors?
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
- Cressy Snr
- Amstrad Tower of Power
- Posts: 10582
- Joined: Wed May 30, 2007 12:25 am
- Location: South Yorks.
#83 Re: DIY Transistor Amp Using NVA Boards
Oh yes indeed!
Sgt. Baker started talkin’ with a Bullhorn in his hand.
-
- Shed dweller
- Posts: 2300
- Joined: Fri Aug 03, 2007 10:57 am
- Location: From the land of the Bodgers
#84 Re: DIY Transistor Amp Using NVA Boards
Given the layout you could build a Mu metal box inside the case to place them in...
Only the Sith deal in absolutes.
- Cressy Snr
- Amstrad Tower of Power
- Posts: 10582
- Joined: Wed May 30, 2007 12:25 am
- Location: South Yorks.
#85 Re: DIY Transistor Amp Using NVA Boards
Sounds like a plan if I can get the boards going in the first instance without blowing them up. I’m not holding my breath, but we’ll see if they stay in one piece first.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
- Cressy Snr
- Amstrad Tower of Power
- Posts: 10582
- Joined: Wed May 30, 2007 12:25 am
- Location: South Yorks.
#86 Re: DIY Transistor Amp Using NVA Boards
OK, here is the progress so far:
Output transistors fitted to heat sinks. Better fixing brackets for the heatsinks were made up, creating extra work, but the heatsinks are far more solidly connected to the black aluminium plate than they were.
Back panel.
Just the rectifiers to fit; one behind each pair of caps, plus the electrical safety earth wire needs bolting to the base of the case. This is being built to class 1 standard.Output transistors fitted to heat sinks. Better fixing brackets for the heatsinks were made up, creating extra work, but the heatsinks are far more solidly connected to the black aluminium plate than they were.
Back panel.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
- Cressy Snr
- Amstrad Tower of Power
- Posts: 10582
- Joined: Wed May 30, 2007 12:25 am
- Location: South Yorks.
#87 Re: DIY Transistor Amp Using NVA Boards
There will be four corresponding holes punched into the lid of the case, backed by an aluminium mesh.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
- Cressy Snr
- Amstrad Tower of Power
- Posts: 10582
- Joined: Wed May 30, 2007 12:25 am
- Location: South Yorks.
#88 Re: DIY Transistor Amp Using NVA Boards
I’ve ended the day utterly pissed off!
Two power supplies all wired in. Fire up to check it functions and the large transformer goes beserk, drawing massive current, yet voltages on its associated caps check out fine, then smoke wisps, so switch off. Small psu is fine. The large transformer is also fine; until it is in circuit.
Can’t find any shorts, but something is causing the large current draw. All I can think of is either a duff cap or bridge rectifier; there’s nothing else, unless I’ve somehow created a shorted turn with the fixing bolt. Either way the fault has got to be found or I’m going to have to abandon the dual power supply idea.
I don’t get it. I have put three power supplies on the OTL with zero issues. But solid state is proving a complete bastard. Is there some black art regarding multiple bipolar PSUs that I’m not in on?
Two power supplies all wired in. Fire up to check it functions and the large transformer goes beserk, drawing massive current, yet voltages on its associated caps check out fine, then smoke wisps, so switch off. Small psu is fine. The large transformer is also fine; until it is in circuit.
Can’t find any shorts, but something is causing the large current draw. All I can think of is either a duff cap or bridge rectifier; there’s nothing else, unless I’ve somehow created a shorted turn with the fixing bolt. Either way the fault has got to be found or I’m going to have to abandon the dual power supply idea.
I don’t get it. I have put three power supplies on the OTL with zero issues. But solid state is proving a complete bastard. Is there some black art regarding multiple bipolar PSUs that I’m not in on?
Sgt. Baker started talkin’ with a Bullhorn in his hand.
- Mike H
- Amstrad Tower of Power
- Posts: 20189
- Joined: Sat Oct 04, 2008 5:38 pm
- Location: The Fens
- Contact:
#89 Re: DIY Transistor Amp Using NVA Boards
That told you didn't it
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
- Mike H
- Amstrad Tower of Power
- Posts: 20189
- Joined: Sat Oct 04, 2008 5:38 pm
- Location: The Fens
- Contact:
#90 Re: DIY Transistor Amp Using NVA Boards
Steve C, welcome to my world, that was me in the 1970's. Walking home from college Friday night I'd pop into Bi-Pre-Pak in West Road, Southend, and get four if not six power transistors for whichever amp prototype I'm going to be working on over the weekend, cos was a pretty safe bet I'd blown up at least two of them.
Have a break and get back to it later with a fresh pair of eyes.
Have a break and get back to it later with a fresh pair of eyes.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."