30-03-2017, 10:25 AM
(This post was last modified: 30-03-2017, 10:27 AM by Diabolical Artificer.)
Progress report. I've wound the mains transformer using a toroidal core out of the SA900C amplifier I replaced the tfmr's on. As money is always tight and I like to recycle it made sense to re-use it. The toroid is rated for 625VA which is more than adequate as I calculated I'd need a 500VA tfmr. I overwound it using heavier gauge wire than needed.
So we have winding's as follows - actual DC/wot's needed in bracket's) - a 370v 700mA bifilar wound HT winding tapped at 350v (430/450 @ 640mA), 60v 80mA (40v 10mA and 80v 11mA) for neg bias and the CCS for the LTP, 15v 1A (12.6v 300mA) for the front end and LTP htr's, 6.3v AC 600mA and finally two 18.9v 4A AC (18.9v @ 1.5A). I'll have to use another smaller tfmr for relay/metering/whatnot.
After much thought I decided on an unconventional way to house the amplifier. I think the "whacking everything on an upside down pudding tin" approach with valve's like god's on an alter isn't for me. With a big amp like this the pudding tray/tin or chassis would have to be huge. the big amp's I've seen like this look c*** IMHO. I love how Tek built their old 500 series scopes and have a scrap 545A so decided to build the actual amplifier like a Tek plugin with the PSU etc sitting behind. The amp with be able to be pulled out for working on (but will need an extender cable).
I've put in a lot of thunking on aspect's like layout, cooling, access, grounding, neatness etc. I've built a mock up - see pic's - to iron out any possible problem's. I think better with my hand's and am not one to sit and draw a precise technical drawing. This way if I drill holes in the wrong place it won't matter.
As you see I've re used some of the ceramic wafer's out of the Tek scope ( there was no way it could be easily restored, I thought hard before taking it apart), this way it will live on in some form.
Pic one iis the underside of the amp, the opt instead of being central will go to one side.
Pic two 120w ish amplier a la Tek Plugin.
Pic three, as amp "plugin" will sit in chassis; two will fit in, PSU's int back connected by plugs/connectors.
Pic 4 PSU at present, more work to do.
TFL, Andy.
So we have winding's as follows - actual DC/wot's needed in bracket's) - a 370v 700mA bifilar wound HT winding tapped at 350v (430/450 @ 640mA), 60v 80mA (40v 10mA and 80v 11mA) for neg bias and the CCS for the LTP, 15v 1A (12.6v 300mA) for the front end and LTP htr's, 6.3v AC 600mA and finally two 18.9v 4A AC (18.9v @ 1.5A). I'll have to use another smaller tfmr for relay/metering/whatnot.
After much thought I decided on an unconventional way to house the amplifier. I think the "whacking everything on an upside down pudding tin" approach with valve's like god's on an alter isn't for me. With a big amp like this the pudding tray/tin or chassis would have to be huge. the big amp's I've seen like this look c*** IMHO. I love how Tek built their old 500 series scopes and have a scrap 545A so decided to build the actual amplifier like a Tek plugin with the PSU etc sitting behind. The amp with be able to be pulled out for working on (but will need an extender cable).
I've put in a lot of thunking on aspect's like layout, cooling, access, grounding, neatness etc. I've built a mock up - see pic's - to iron out any possible problem's. I think better with my hand's and am not one to sit and draw a precise technical drawing. This way if I drill holes in the wrong place it won't matter.
As you see I've re used some of the ceramic wafer's out of the Tek scope ( there was no way it could be easily restored, I thought hard before taking it apart), this way it will live on in some form.
Pic one iis the underside of the amp, the opt instead of being central will go to one side.
Pic two 120w ish amplier a la Tek Plugin.
Pic three, as amp "plugin" will sit in chassis; two will fit in, PSU's int back connected by plugs/connectors.
Pic 4 PSU at present, more work to do.
TFL, Andy.
