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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
Posted to sci.electronics.repair
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Valve/tube screening can problem
Mesa Nomad 55 with one of the 12AX7 snow capped and a neat ring around the
top of the glass envelope. Obviously due to the bed-spring gauge of spring inside the can. 2Kg to halve the spring length, probably 2/3 compression in use. No point in replacing without changing all the springs or something. How to reform a weak straight compression spring (easily available) to conical or otherwise fit inside the can and the glass touching end be centrally posistioned. ? Secondly there is no dedent to stop the cans rotating other than use of heavy springs - catch 22. What to do, retrofit, without taking the amp apart to get to the inside of the chassis. So far I've discovered a working , but not elegant solution. One of those brass-eyelet hand pincer/dies pushing the die pin outwards to deform a pip in the aluminium, outwards, 1/4 way round so it locates in one of the 2 chassis cutaways. Needs some rubber padding on the outside so the other anvil half does not excessively damage that local area. Any other solutions anyone else has found, particularly forming or re-forming spring metal to something like conical My attempts are very wonky. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#2
Posted to sci.electronics.repair,rec.antiques.radio+phono
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Valve/tube screening can problem
N_Cook wrote in message ... Mesa Nomad 55 with one of the 12AX7 snow capped and a neat ring around the top of the glass envelope. Obviously due to the bed-spring gauge of spring inside the can. 2Kg to halve the spring length, probably 2/3 compression in use. No point in replacing without changing all the springs or something. How to reform a weak straight compression spring (easily available) to conical or otherwise fit inside the can and the glass touching end be centrally posistioned. ? Secondly there is no dedent to stop the cans rotating other than use of heavy springs - catch 22. What to do, retrofit, without taking the amp apart to get to the inside of the chassis. So far I've discovered a working , but not elegant solution. One of those brass-eyelet hand pincer/dies pushing the die pin outwards to deform a pip in the aluminium, outwards, 1/4 way round so it locates in one of the 2 chassis cutaways. Needs some rubber padding on the outside so the other anvil half does not excessively damage that local area. Any other solutions anyone else has found, particularly forming or re-forming spring metal to something like conical My attempts are very wonky. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ This is a work-around for the springs. May have gone too far the other way 200gm rather than 2Kg. Expanded aluminium mesh (for continued ventillation through the central hole in the can) cut to a square to squash inside the can. Straught 12mm diameter compression spring. One end , the last 2mm , bend to point axially. Thread that end through a suitable hole inthe mesh and push around for a near circle and feed back through the mesh with the return poking through the adjascent hole. Curl back the corners of the mesh enough to push into the can. Use a din connector cover to go over the spring and push the mesh into the can. Then with din cover in place , use a screwdriver to push the mesh down to wedge into the can top. The spring then stays centrally and axially located . The eyelet pliers fudge works quite well for dedenting the cans, combined with the existing "O" ring antivibration ring. rarp added as probably relevant -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#3
Posted to sci.electronics.repair
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Valve/tube screening can problem
"N_Cook" wrote in message ... Mesa Nomad 55 with one of the 12AX7 snow capped and a neat ring around the top of the glass envelope. Obviously due to the bed-spring gauge of spring inside the can. 2Kg to halve the spring length, probably 2/3 compression in use. No point in replacing without changing all the springs or something. How to reform a weak straight compression spring (easily available) to conical or otherwise fit inside the can and the glass touching end be centrally posistioned. ? Secondly there is no dedent to stop the cans rotating other than use of heavy springs - catch 22. What to do, retrofit, without taking the amp apart to get to the inside of the chassis. So far I've discovered a working , but not elegant solution. One of those brass-eyelet hand pincer/dies pushing the die pin outwards to deform a pip in the aluminium, outwards, 1/4 way round so it locates in one of the 2 chassis cutaways. Needs some rubber padding on the outside so the other anvil half does not excessively damage that local area. Any other solutions anyone else has found, particularly forming or re-forming spring metal to something like conical My attempts are very wonky. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Maybe give this a try lad http://www.imagefap.com/image.php?id=1988478267 Always works wonders for me! Kirk Johnson "EXTREME Stretching Specialist" |
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