|
Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE! |
|
Thread Tools |
23rd Jun 2021, 12:38 am | #1 |
Nonode
Join Date: May 2016
Location: Cornwall, UK.
Posts: 2,339
|
Metal Bashing: Uher Miniline 220V Bucking Box
Our mains is quite high (at present 247V) and I noticed my Uher Miniline stack, marked 220V, was getting very hot in use.
The advice from Members here coalesced around a bucking transformer. After reading up on the Elliot Sound Products page on these, I wired a Velleman 209009C dual 9V transformer in ESP's recommended autotransformer configuration. It wasn't going to fit in the tight casings of the Miniline stack, so I took advantage of the relaxed Covid restrictions to get access to a workshop and some metal bashing advice from my brother, planning to make a case that matched the Uher aesthetic. After calculating and drawing the folded net on a piece of filing cabinet panel, I snipped with shears and a Monodex nibbler, before filing to the scribed lines. Lockdown has taught me basic welding, and I've made a bender to help put new sills on my car. This box was its first test. While a bit indelicate, I eventually got the folds in the right place, with only some areas that required soldering and filing back. |
23rd Jun 2021, 12:47 am | #2 |
Nonode
Join Date: May 2016
Location: Cornwall, UK.
Posts: 2,339
|
Re: Metal Bashing: Uher Miniline 220V Bucking Box
The top was a single piece bent to form three sides, with similar small screws used to hold it down as on the rest of the Uher stack.
A few coats of high-build primer, and Halfords Satin Black made quite a good match. The electrical innards are simple - an IEC plug; the neon bulb and clip-in orange shade from a broken shower pull-switch; the transformer and a Cannon LNE mains outlet, where the Uher Z140 power amplifier is connected. I used these because I happened to have some, they were unusual enough not to be used on anything else I'd ever seen, and they are around the same period as the stack. For my further amusement, I am planning to make some decals or screen-print similar legends on the top to make it appear more like a genuine artefact. |
23rd Jun 2021, 12:49 am | #3 |
Nonode
Join Date: May 2016
Location: Cornwall, UK.
Posts: 2,339
|
Re: Metal Bashing: Uher Miniline 220V Bucking Box
Pictures in situ.
I'm quite pleased with this, as my first foray into metal-bending. I need to get better at not expecting a first try to be spot on, especially with rudimentary tools and no experience. The paint covers a multitude of sins, and the perfect is the enemy of the good. |
23rd Jun 2021, 1:19 am | #4 |
Octode
Join Date: Jul 2018
Location: Worthing, West Sussex, UK.
Posts: 1,003
|
Re: Metal Bashing: Uher Miniline 220V Bucking Box
That is a fabbo end product- well done mate!
|
23rd Jun 2021, 6:08 am | #5 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,902
|
Re: Metal Bashing: Uher Miniline 220V Bucking Box
I might have missed seeing it, but is there a fuse?
David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
23rd Jun 2021, 8:43 am | #6 |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,604
|
Re: Metal Bashing: Uher Miniline 220V Bucking Box
Excellent and professional job, well done Uncle Bulgaria, has it cured the hot running issue ?
David |
23rd Jun 2021, 11:59 am | #7 | |
Nonode
Join Date: May 2016
Location: Cornwall, UK.
Posts: 2,339
|
Re: Metal Bashing: Uher Miniline 220V Bucking Box
Thank you for the kind comments! It is nice to show and tell to people who aren't your family.
I haven't tested it for more than a few minutes yet - I need to hook up the 'speakers and demote the Ferrograph from record duty for a little while. Luckily there's a Bandcamp order on the way...or the World Test Final's looking interesting... Quote:
The Z140, and by extension the stack, are isolated from mains earth. The original mains cable, which now terminates in the Cannon socket, is two-core. As the new bucking box is metal, I've tied it to the safety earth from the IEC with a star washer and ring terminal under the transformer attachment point, thinking that was sufficient for the fault conditions I could foresee. If more august Members think it advisable, there is room inside the box for an in-line fuse - I'm loath to drill the case again for a panel-mount one! |
|
23rd Jun 2021, 12:49 pm | #8 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,902
|
Re: Metal Bashing: Uher Miniline 220V Bucking Box
I was just thinking in case it got re-purposed, used for other things or went out of your hands. 13A plugs are notorious for people shoving any fuse they can find inside. I understand the entire rock music industry was founded on the perfect fit of a 1/4 inch jack plug barrel section into the fuse clips of a plug....
David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
23rd Jun 2021, 5:20 pm | #9 |
Hexode
Join Date: Jul 2009
Location: Wokingham, Berkshire, UK.
Posts: 437
|
Re: Metal Bashing: Uher Miniline 220V Bucking Box
I have to admit being a bit unhappy about the Cannon power line connector as it is non approved.
John |
23rd Jun 2021, 7:05 pm | #10 |
Dekatron
Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 4,311
|
Re: Metal Bashing: Uher Miniline 220V Bucking Box
If one is fitted then there is an interesting question concerning where it should go and what rating it should be. Personally I'd fit a fuse in the incoming mains wiring, suitably rated to protect the bucking transformer secondary from an over-current fault.
This might well not disconnect the transformer primary, though, in the event of a fault within it (the primary). A lower-rated fuse could be added, just in series with the primary, to give that protection. But then the consequences of that fuse opening would have to be considered. Now the secondary would essentially become an inductor, perhaps with a reactance high enough that a lot more than 10VAC appears across it. Transformer action would result in a very high voltage appearing across the primary. What harm might that do ? Is the small primary fuse actually likely to do more harm than good ? I'm not sure there's a simple solution to this problem with the bucking transformer scheme. I've just realised though that any discussion of it might not really belong in a thread about metal-bashing ... Cheers, GJ
__________________
http://www.ampregen.com |
23rd Jun 2021, 8:13 pm | #11 |
Octode
Join Date: Dec 2017
Location: Morden, Surrey, UK.
Posts: 1,561
|
Re: Metal Bashing: Uher Miniline 220V Bucking Box
|
23rd Jun 2021, 8:40 pm | #12 | |
Guest
Posts: n/a
|
Re: Metal Bashing: Uher Miniline 220V Bucking Box
Quote:
|
|
24th Jun 2021, 12:09 pm | #13 | |
Nonode
Join Date: May 2016
Location: Cornwall, UK.
Posts: 2,339
|
Re: Metal Bashing: Uher Miniline 220V Bucking Box
Thanks for the comment, John. The connector is solidly built and originally rated for mains, and its 1970s-ness was part of the reason I chose it. Its locking mechanism is ergonomically pleasing and secure. Certainly easier to use than an IEC! In this case it's passing less than an amp, so I don't think it's a weak link.
Quote:
Radio Wrangler's point about a subsequent user had crossed my mind, but as it's unlikely to leave my hands for the next half-century I am not very worried. Besides, the case will have labelling detailing the fuse requirements, just like a Uher Z131 cassette power supply. Then if the value's wrong (as it was in the Z131 I have here) at least it's obvious. |
|