PPX1200 humming |
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scott_fury
Registered User Joined: 28 October 2012 Location: Bristol Status: Offline Points: 319 |
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Hopefully it’s something simple, but old sod and his law has a habit of introducing himself when I work on stuff. Currently have 4:1 ratio of fixing and breaking things, so doing good at the moment. Fingers crossed. I assumed they were the sort of things that would turn up inside my old Commodore 64, but ‘cloak and dagger’ sounds way more interesting than enabling teens of the 80’s to play International Karate +.
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Sonic the hedge
Registered User Joined: 12 May 2020 Status: Offline Points: 161 |
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I find the problem with testing 'on board' is it's often hard to tell if you are getting an (in)accurate reading due to other components on the PCB in parallel etc. Albeit heatsinked transistors can be tedious to remove screws and nuts so it's easier to isolate the transistor for testing 'on board' by disconnecting surrounding components. Resistors and wire links are my favourite cos you can desolder just one end and leave it flying. Anything else should come off the PCB easily with a solder sucker, asuming it's old through-hole stuff with real lead solder, but we are talking PPX One of the best sounding, most robust amps ever built IMHO. All the more amazing since Citronic was aimed at the 'Disco' sector.
Edited by Sonic the hedge - 20 May 2020 at 7:09am |
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scott_fury
Registered User Joined: 28 October 2012 Location: Bristol Status: Offline Points: 319 |
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Thanks for the tips. I think my issue is just a lack of experience. I’ve been a domestic electrician, auto-electrician, can mig and tig weld..... but I can’t solder without ballsing things up. Just can’t seem to hang of it. Got a suction tool and a couple of different wattage irons. Tried making basic circuits, bat detectors etc :) Can’t do it. The idea of replacing a component on a circuit board gives me a bit of the fear! I shall perservere as I really want to do it, but may need a dummy item to practice on first 😅
Edited by scott_fury - 20 May 2020 at 8:12am |
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Sonic the hedge
Registered User Joined: 12 May 2020 Status: Offline Points: 161 |
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Yeah practice is the key, I have been buggering up electronics since I was a kid Defo worth getting some old knackered hi-fi etc just to practice soldering on, you may well find that taking away the fear of breaking something actually improves your confidence and technique quite quickly.
Edited by Sonic the hedge - 20 May 2020 at 8:45am |
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jbl_man
Moderator Group Joined: 12 January 2005 Location: London. Status: Offline Points: 11154 |
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One thing i would mention, even after completely de-soldering components on these old Citronic amps,they were very tightly fitted,(they stay in place firmly without any solder at all), it's almost like pulling teeth.
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Be seeing you.
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Sonic the hedge
Registered User Joined: 12 May 2020 Status: Offline Points: 161 |
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Are the legs folded over to hold them in? That can be a b@stard! With practice you can heat the solder, bend the leg straight and push it through the board, all in one go using the tip of the iron. Use a small angled tip, use the tip like a wedge/lever to lift the leg, then a slight twist of the tip to push the leg through the board. Obviously for transistors, ICs etc. need to straighten all the legs before it will come out. Probably not best advice for a complete novice though! Have to be quick so you don't overheat the component.
Edited by Sonic the hedge - 20 May 2020 at 2:04pm |
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scott_fury
Registered User Joined: 28 October 2012 Location: Bristol Status: Offline Points: 319 |
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So I got the 1600 out last night to test the transistor for this clip LED, but unfortunately noticed something was wrong with one of the transformers.
The glued piece in the centre of the coil has broken and the coil is now loose. I have looked at the 1200 schematics and I can see there is a 125degree trip labelled on the transformers which i guess is a thermal cut out. It looks like the trip and transformer are all glued to mounting bolt? I’m going to test it today to see if it still works as it should, but is it possible to glue this back together, and if so, which glue would do the best job...... some sort of 2-part araldite maybe?
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kedwardsleisure
Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4938 |
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I think originally it would be a 2-part epoxy or polyurethane hard potting compound. Is that the reason yours was buzzing?
I've used polyester filler in an emergency for the big transformers in the past. https://www.rapidonline.com/robnor-px804c-bk-500g-potting-compound-twin-pack-500g-87-0216 |
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Kevin
North Staffordshire |
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scott_fury
Registered User Joined: 28 October 2012 Location: Bristol Status: Offline Points: 319 |
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Thanks for the link. I imagine it’s easy enough to stick the trip back to the bolt, but getting something to stick to the coil covering may be a little tricky.
I imagine it had a knock upside down maybe. I don’t know if this sort of thing is common but I’m going to have to be more vigilant in the future.
Nope. This is the 1600. The 1200 was buzzing.
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kedwardsleisure
Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4938 |
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might be worth opening a new thread for a different amp so it avoids confusion in the future
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Kevin
North Staffordshire |
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