Re: [Repeater-Builder] Micor Mobile 110 watt amp

[Kevin Custer]

[EMAIL PROTECTED] wrote: Kevin,     Just got a Micor mobile repeater going. Was planning on running 110 watt amp around 65 watts. Installed a 120 vac squirrel cage fan right next to side heatsink. It is controlled via thermo switch mounted inside radio on heatsink casting. This fan nearly blows the paint off the heatsink fins. Also drilled 4  1/4 inch holes between heatsink fins to allow some forced air to enter radio and pass over power amp transistors. Did someone say to run 110 watt amp at full bore and to keep high capacity fan on it because PA is temp controlled?  Is this ok to do this? I would like to run my 110 watt amp at its rated power output if it would last a decent amount of time in repeater service. The method you have chosen to cool your PA *should* prove to be reliable.  The only difference between the VHF Micor Mobile and Station 110 watt PA is the mass of the heatsink and the thermistor in the Power Set Control board.  If you are able to keep the PA transistors cool, running the mobile vhf PA wide open should prove to be reliable.  If the fan (blower) quits and the PA gets hot, the thermistor in the PSC board will throttle back the PA to a safe dissipation.  The Station PA omits this temperature part. On that note,  I built a UHF repeater from a Micor Station.  Someone had stolen the PA before I had obtained it.  As a *temporary* fix, I installed a modified 75 watt UHF Micor Mobile PA.  I removed the very first (low level) stages so the 2 watts from the tripler would properly drive it.  I installed a 220 volt muffin fan on it run from 110 volts.  The fan and PA are still on the repeater, providing more than 10 years of continuous duty type operation, without failure.  While the UHF Micor PA's aren't (in my opinion) as robust as the VHF and HF units, they can be reliable. As others have said, running a Class C power amplifier at less than 2/3 or 1/2 its rated output power is usually asking for trouble, so unless you want 50 watts and are willing to change out the PA board to a 45 or 60 watt unit, I'd run her full blast and keep the bearings oiled in the blower. Kevin Custer Yahoo! Groups Links To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/   To unsubscribe from this group, send an email to: [EMAIL PROTECTED]   Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.