Hi Jeff, Thanks for the reply. I too, thought that it was drawing a little too much current. The unit has a sticker on it that says 450 to 470 and I'm testing it with a MastrII exciter on 442.800. So, you're probably right in what's going on.
I'm going to see if I have an ICOM for my 449.875 repeater and if so, test it on that frequency. Hopefully, I'll see the current draw go down and then know for sure what's going on. If I want the caps changed, is there anyone in particular at Crescend I need to talk to? I wasn't aware that they would support the Milcom line. Thanks!! Adam N2ACF On 6/6/2010 10:26 AM, Jeff DePolo wrote: > 28-29 amps is on the high side. Are you using the amp at more than maybe 5 > MHz or so from the original frequency? Some of the Milcom/Crescend amps are > tunable, but many used fixed-value metal-clad mica capacitors in the base > and collector matching. The values of the caps and/or their placement along > the microstrips is varied depending on frequency. > > While you could experimentally determine the right values/placements using > common sense techniques, it's probably easier just to send it to Crescend to > have them move it to your frequency. I have a 350 watt Vocom UHF amp that > had the same issue - fixed caps. After counting how many caps I'd have to > futz with, I concluded it was cheaper to send it to them and letthem do it > for $200. They turned it around in about a week. > > If you need 250 mW in and 100 watts out, a Mastr II PA would do you nicely > (and cheaply!). > > --- Jeff WN3A > > > > >> -----Original Message----- >> From: Repeater-Builder@yahoogroups.com >> [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Adam Feuer >> Sent: Saturday, June 05, 2010 11:35 PM >> To: Repeater-Builder@yahoogroups.com >> Subject: Re: [Repeater-Builder] Re: Milcom International UHF PA >> >> >> >> Hi Alex, >> >> Thanks for the reply! Your description of the pots was great but I >> don't see ANY tuning caps on any boards in this amp. There's a 10watt >> board that feeds a 65w board. Then, this 65w board gets split to feed >> two more 65w boards which get combined as the final output. >> >> I can easily set R10 to 100 watts but I would like more info on the >> tuning caps if it's applicable to this amp. At 100 watts the amp is >> drawing about 28 to 29 amps. I may be incorrect but I thought >> some of my >> other 250mw in 100w out PA's only draw 22 amps. >> >> Thanks again! >> >> Adam N2ACF >> >> On 6/5/2010 6:04 PM, opelgtalex wrote: >> >>> Adam- >>> R10 controls the bias voltage to the first stage driver- >>> >> this sets the power out of the amp. Turn this pot down (lower >> the PA output) peak out all tuning caps starting at the 1st >> stage, then the 2nd and on to the 4 driver boards. Once all >> tuning caps are adjusted for peak output, then adjust R10 for >> the amplifiers rated power out (100W in your case). >> >>> R9 controls the foldback power in case of a high temp >>> >> condition the power output is cut by 3dB- the thermal switch >> is located just below the control board. >> >>> As per manual R9 is adjusted by removing power from the >>> >> cooling fan, key the RF source, wait for the unit to reach >> 135deg F and adjust R9 for 3dB below rated amp output- this >> is per manual. >> >>> Hope this helps, >>> Alex >>> >>> --- In Repeater-Builder@yahoogroups.com >>> >> <mailto:Repeater-Builder%40yahoogroups.com> , Adam >> Feuer<feu...@...> wrote: >> >>> >>>> Hello All, >>>> >>>> I have a Milcom International UHF PA on the bench. Model number is >>>> P12-O5HA1-C1 rated at 250mw in with 100w out. I'm trying >>>> >> to identify >> >>>> what two pots (R9& R10) do on a board that "seems" like a control >>>> board. Both pots appear to vary the output power and current draw, >>>> although one does it more dramatically than the other. >>>> >>>> Anyone have a manual or information for this PA? Any help would be >>>> greatly appreciated. >>>> >>>> Thanks!! >>>> >>>> Adam N2ACF >>>> >>>> >>>> >>> >>> >>> ------------------------------------ >>> >>> >>> >>> Yahoo! Groups Links >>> >>> >>> >>> >>> >>> >> >> >> >> >> > > > ------------------------------------ > > > > Yahoo! Groups Links > > > > >
