Re: [Drakelist] More MN-4C saga
The drug store has 99% Isopropyl alcohol..I suspect it is less expensive than drinking alc and is good for any technical cleaning. Be sure it is the 99% stuff and not the lesser that has more water in it. Also..talcum powder put on a dampened switch section will draw out material and moisture from the ceramic pores. After allowing it to dry, or baking it at low temp, the talcum powder can be blown of with compressed air. It will help to draw any carbon particles out of the ceramic. If it is still visible after all that, an application of HV varnish over that area can help to prevent recurrence of the problem. FWIW Curt (the other Curt) KU8L Al Parker wrote: Hi Curt, Yes, that could be the problem, the black stuff is quite conductive, as it's carbon. I think you've said you've disassembled things, so have the switch out. If so, first just try to brush any loose stuff away, then I'd take the switch to the sink & use some hand dishwashing soap and a toothbrush, and flowing water, to scrub the area as well as you can. Then use some alcohol, pure if possible, and with a cleaned toothbrush do some more scrubbing. Blow it dry with compressed air if you have it, then let it dry in some heat, up to 140F or so is OK. Give it a day or so to dry. Then just maybe, you've gotten the worst of the carbon out, but it does get into porous ceramic and it's hard to get out. For "pure" alcohol, I use "Everclear" shich is available quite cheaply from the local ABC/liquor store. Half a pint can last years, if you don't mix it with your favorite mixer to assuage your grief after you find the cleaning process hasn't been successful ;-) Everclear is 180-190 proof I think, 90+% alcohol, don't drink it straight. 73, Al, W8UT www.boatanchors.org www.hammarlund.info "There is nothing -- absolutely nothing -- half so much worth doing as simply messing about in boats" Ratty, to Mole On 10/14/2010 10:26 AM, Curt wrote: Hello Al, Absolutely, there is a blackened area in the vicinity of where the 160M cap is located. The original cap was blackened as well, and originally I thought it was the problem. Would that area cause symptoms like am experiencing? The switch decks are ceramic, rather porous. How to clean? 73, Curt KB5JO ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] More MN-4C saga
I have cleaned the medal disc part, that would not clean up with any chemical, with the eraser on a pencil. It did a GREAT job. I have tried to clean the ceramic part with alcohol. But with limited success. Hope this helps. KB8NXO On Thu, Oct 14, 2010 at 10:28 AM, Curt wrote: > What method can be used to restore a porcelain switch deck with carbon > streaking? The bandswitch on this MN-4C shows blackening near the 160M > capacitor position. > > 73, Curt KB5JO > > ___ > Drakelist mailing list > Drakelist@zerobeat.net > http://mailman.zerobeat.net/mailman/listinfo/drakelist > > ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] More MN-4C saga
Hi Curt, Yes, that could be the problem, the black stuff is quite conductive, as it's carbon. I think you've said you've disassembled things, so have the switch out. If so, first just try to brush any loose stuff away, then I'd take the switch to the sink & use some hand dishwashing soap and a toothbrush, and flowing water, to scrub the area as well as you can. Then use some alcohol, pure if possible, and with a cleaned toothbrush do some more scrubbing. Blow it dry with compressed air if you have it, then let it dry in some heat, up to 140F or so is OK. Give it a day or so to dry. Then just maybe, you've gotten the worst of the carbon out, but it does get into porous ceramic and it's hard to get out. For "pure" alcohol, I use "Everclear" shich is available quite cheaply from the local ABC/liquor store. Half a pint can last years, if you don't mix it with your favorite mixer to assuage your grief after you find the cleaning process hasn't been successful ;-) Everclear is 180-190 proof I think, 90+% alcohol, don't drink it straight. 73, Al, W8UT www.boatanchors.org www.hammarlund.info "There is nothing -- absolutely nothing -- half so much worth doing as simply messing about in boats" Ratty, to Mole On 10/14/2010 10:26 AM, Curt wrote: Hello Al, Absolutely, there is a blackened area in the vicinity of where the 160M cap is located. The original cap was blackened as well, and originally I thought it was the problem. Would that area cause symptoms like am experiencing? The switch decks are ceramic, rather porous. How to clean? 73, Curt KB5JO ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] More MN-4C saga
What method can be used to restore a porcelain switch deck with carbon streaking? The bandswitch on this MN-4C shows blackening near the 160M capacitor position. 73, Curt KB5JO___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] More MN-4C saga
Hi Curt, Can you see a black, carbon, streaks or areas on any of the wafers? Could be a resistance path between contacts. I expect the wafers are ceramic, you may or may not be able to clean them, depending upon how porous they are. 73, Al, W8UT www.boatanchors.org www.hammarlund.info "There is nothing -- absolutely nothing -- half so much worth doing as simply messing about in boats" Ratty, to Mole On 10/13/2010 9:19 PM, Curt wrote: After dismantling the tuner (again), the problem seems associated with the bandswitch/coil assembly. Somehow there seems to be low RF impedance to ground for the 40M, 80M and 160M positions. When listening to a signal on 40M, signal strength is high on the 20M position, then drops dramatically when the bandswitch is moved to 40M. It's as if there was a large unseen bypass capacitor in the circuit. All of the caps are new correct value capacitors. The tuner works properly on 20M, 15M and 10M. On the lower bands, no setting of the resistive/reactive controls will tune out the mismatch. What bandswitch failure mode would behave in this way? 73, Curt KB5JO ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] More MN-4C saga
After dismantling the tuner (again), the problem seems associated with the bandswitch/coil assembly. Somehow there seems to be low RF impedance to ground for the 40M, 80M and 160M positions. When listening to a signal on 40M, signal strength is high on the 20M position, then drops dramatically when the bandswitch is moved to 40M. It's as if there was a large unseen bypass capacitor in the circuit. All of the caps are new correct value capacitors. The tuner works properly on 20M, 15M and 10M. On the lower bands, no setting of the resistive/reactive controls will tune out the mismatch. What bandswitch failure mode would behave in this way? 73, Curt KB5JO___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
