All the supplies used are trimmable so with a meter at the console power rails I trim for exact required voltage - that’s why they’re staggered in the rack drawer to be able to access wiring connection screws and the trimmers.
~250kHz pings from neve 1073 type line output stage
- Thread starter HenryL
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Nice. Forbidden Planet ?!
A bit over my budget, sadly
If this was a more perfectionist project, or building something from scratch, rather than trying to make something nicer out of what I've already got - I would probably do the kinds of things you've suggested. But I think apart from the switching interference - soon to be completely eliminated...the power supplies are fine.
Yes I'd go for a bridge, but in their defence it's very well smoothed with the zener regulators, filter cap stages, further 24V regulator etc. it's pretty quiet in my books. I don't like the smoking hot dropper but I'm going to fix that.
The last scope pic was under full/normal quiescent current draw from the preamp (albeit no phantom draw in that example). There shouldn't be a significantly greater load when carrying a signal (class-A). If that's what you meant?
A bit over my budget, sadly
If this was a more perfectionist project, or building something from scratch, rather than trying to make something nicer out of what I've already got - I would probably do the kinds of things you've suggested. But I think apart from the switching interference - soon to be completely eliminated...the power supplies are fine.
Yes I'd go for a bridge, but in their defence it's very well smoothed with the zener regulators, filter cap stages, further 24V regulator etc. it's pretty quiet in my books. I don't like the smoking hot dropper but I'm going to fix that.
The last scope pic was under full/normal quiescent current draw from the preamp (albeit no phantom draw in that example). There shouldn't be a significantly greater load when carrying a signal (class-A). If that's what you meant?
Yes - as long as there’s no significant change in the ringing with different loads and input frequencies. You could load up the 48V at the same time with a 3K9 which would draw 12.3mA just under 0.6W - it depends on the value of the phantom feed resistors as to how much current you can draw before the voltage drops below usual tolerance of + 4V.
<Insert 2 weeks motorcycle tour here> Have carried out the remaining planned mods to the PSU and am now happy that the spiking/ringing interference has been sufficiently subdued. If all the audio board/connections are disconnected then a very small regular wobble can still be picked up parasitically by the scope connected to the output socket, but as soon as the output tx is connected to the socket then it is soaked up and no longer visible, and does not appear under full load.
In addition to the earlier measure of swapping the diodes for faster types the final solution was, as discussed, adding series resistance between the pwr tx and the input of the rectification stages. I also split the main filter/dropping resistor in the 24V supply across both +ve and ground lines, putting about 20% of it in the single ground path.
I'll post the details of the mods in case anyone else is playing around with one of these units.
In addition to the earlier measure of swapping the diodes for faster types the final solution was, as discussed, adding series resistance between the pwr tx and the input of the rectification stages. I also split the main filter/dropping resistor in the 24V supply across both +ve and ground lines, putting about 20% of it in the single ground path.
I'll post the details of the mods in case anyone else is playing around with one of these units.
Admiral-dk
Well-known member
Great to hear that you are happy with the end result
Motorcycle Holiday - I wish, but as an unemployed for the time being - that is not on the cards
Where did you go/ride to ?
Per
Motorcycle Holiday - I wish, but as an unemployed for the time being - that is not on the cards
Where did you go/ride to ?
Per
Cheers Per. Yes unfortunately there no longer seems to be any such thing as a cheap holiday, or anything else for that matter!Great to hear that you are happy with the end result
Motorcycle Holiday - I wish, but as an unemployed for the time being - that is not on the cards
Where did you go/ride to ?
Per
The pillion and I took a countryside tour across and up through Wales and back down via a few city-break days in Bristol, with a visit to some relatives on the home track back to Brighton. Youth Hostels mostly, though 'youth' is stretching it a bit in our cases! The weather was a bit of a pain at times in Wales, but a great trip nonetheless...
Admiral-dk
Well-known member
No not unless you have ‘free accommodations with relatives’ (or similar) + cheap gas ….
We were in Wales in 76 during the heatwave (and one day of rain back then would have been nice) - but I remember it as a beautiful trip We did pas Brighton on the way there - admittedly mostly to get to the Beach and Cool Down in the waves. My sister came back a decade later when she studied to be a Chiropractor in Brighton.
I know that my Brother in Law (he’s from Doncaster), would love to show me the whole of UK (if we had the money and time) as we love to ride out together on our Bikes (XL700V in his case and a DL650 is mine).
We were in Wales in 76 during the heatwave (and one day of rain back then would have been nice) - but I remember it as a beautiful trip We did pas Brighton on the way there - admittedly mostly to get to the Beach and Cool Down in the waves. My sister came back a decade later when she studied to be a Chiropractor in Brighton.
I know that my Brother in Law (he’s from Doncaster), would love to show me the whole of UK (if we had the money and time) as we love to ride out together on our Bikes (XL700V in his case and a DL650 is mine).
We want to do more touring ourselves (20yr old Triumph Sprint RS in our case) - my past riding was mainly functional (commuting to work) and this was really our first tour together. The UK is a bit more congested than it was in '76! Enjoyable routes can still be found though. I wouldn't have minded a less heavily loaded - and probably a little easier around towns and obstacles - bike such as one of your V's at times, but still too attached to the old Trumpet
Conclusion of this thread at: Golden Age Projects Pre-73 PSU Schematic and Mods
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