Re: [Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
wb6dgn wrote: There is a process I use to easily see which stage is bad. Reply if you need more help. Maybe you'd consider posting it here? Always looking for better ways to do things. Tom DGN Verify you have drive to the PA by looking to see how much is coming out of it or any filters that follow. Then take the watt meter and put it on the antenna connector and terminate the meter with a suitable load. I use a Bird 43 with matching 100 watt dummy load. I usually start with a 10 or 25 watt slug no matter the size of the PA. If the correct drive is coming from the exciter, make sure the correct voltages are present on the stages of the PA. PNP RF transistors are used in the MICOR VHF PA, so put your thinking cap on upside down. If you have a hand-held radio, tune it to the frequency of the transmitter, and remove the rubber duck and set it off to the side - out of arms reach. Key the defective radio and touch the base of the first transistor in the PA with the metal blade of the Motorola MICOR tuning tool. Watch the S-Meter on the hand-held or listen for quieting. On my Yaesu FT530, I normally get about 1/2 scale S-Meter reading on the base of the first stage. Keeping the radio keyed, touch the collector - the S-Meter reading should be considerably stronger and quieter. If not, you might have found your problem. Anyway, continue doing this down through the stages until you find the bad one - moving the hand-held radio back away as need to add loss. Once you find the stage that has no apparent gain, take a small capacitor (a few hundred pF) and trim the leads so you can use it to bridge across the base to the collector. The leads only need to be long enough to be able to go across the transistor to couple energy at the base to the collector. If the stage is bad, you will see the PA make *some* power - there will be some indication on the watt meter. The transistor, when bridged shows output power, is likely bad and needs replaced. This method can generically to troubleshoot other makes and models of PA's. DISCLAIMER: I have worked on some ill engineered equipment that will go spurious and blow up if you touch one of the RF transistor conductors with some metallic object. This has never happened to me with a MICOR or MASTR II PA, but has with Spectrum and some other junk. Do This At Your Own Risk!! In the MICOR, the first or second stages are usually the culprit, unless something has taken out the final stages, which should only be replaced as a whole, with matched units, if one or more are found to be bad. Kevin Custer
[Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
Bill jawjabill...@... wrote: Apparently no one here got the moto memo on working with giant heat-sinks. I never did during my tenure... memo's usually floated in well after the fact or damage done... First you only need a 30-40 watt iron to work on them as moto did at the factory The secret is .. raising the heat-sink to about 3-400 degrees while you are working on what needs to be done. We Moto types in the field... never had the luxury of all the factory recommended service tools. Half the time I was happy the heater or AC actually worked... : PS .. don't touch it with fingers or arms. This technique also lowers possibility of cracking the ceramics. I usually lay out everything that has to be done in advance with extra planning. Hey, I didn't say it was going to be quick... Bill Atlanta The best way to pre-heat up any PA heat-sink is to place it in Taxi Cab Full Duplex Base-Station service in any large city. Those of you who have experienced the application know exactly what I mean. Yeah, watch your fingers... cheers, s.
[Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
Tom Parker t...@... wrote: Why has no one suggested replacing the guts of this beast with a Mitrek PA? Only if the Mitrek VHF PA is the same animal as some Micor PA's are reported to be. ... and that you can a used Mitrek (with the matching parts) as easily as you can find a used Micor parts radio. Or the converse... s.
[Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
There is a process I use to easily see which stage is bad. Reply if you need more help. Maybe you'd consider posting it here? Always looking for better ways to do things. Tom DGN --- In Repeater-Builder@yahoogroups.com, Kevin Custer kug...@... wrote: radi...@... wrote: Sucess! I completely cleaned and re tinned my Weller 8100 tip, added some solder, and got heat transfer to pop it up. I was not aware of the fish paper that the wires came thru. Now to troubleshoot the amp. It probably has some blown transistors as well as the cooked caps and 12 ohm resistors across some of the finals. We do have a Motorola test set, I have done component level work in the past, but this is out of my league. Kevin, I may take you up on your offer for further help. Thanks to all who responded. 73, Marty Consider obtaining a used MICOR mobile (usually can be gotten for $5 to $50) having a power amplifier board of the desired size and transplant it onto your heatsink. The PA assembly for this mobile radio is identical to the one(s) used on the continuous duty MICOR and MSR2000 power amplifiers. Or, just figure out which stage is bad and replace the transistor(s) that have failed. There is a process I use to easily see which stage is bad. Reply if you need more help. Kevin
[Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
I'm told C4 is much more effective and you need less of it! T. --- In Repeater-Builder@yahoogroups.com, Gordon Cooper zl...@... wrote: Maybe a little Black Powder might be needed? Gordon ZL1KL Tauranga N.Z.
Re: [Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
On 8/2/2010 11:15 PM, skipp025 wrote: ... The entire project including obtaining the parts from recycled radios takes me about 4.5 hours with beverage of choice and some decent AM Talk-Radio playing at low back-ground volume level (no, not the right-wing whack job stuff). As opposed to the left-wing whack job stuff? ;cD Once you've had to do this type of Motorola PA repair, you more fully appreciate trying to keep the amplifier happy and cool. Boy, ain't that the truth!!! My only other comment-it's not absolutely mandatory, but if you can get silver solder, use it.
[Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
Apparently no one here got the moto memo on working with giant heat-sinks. First you only need a 30-40 watt iron to work on them as moto did at the factory The secret is.. raising the heat-sink to about 3-400 degrees while you are working on what needs to be done. PS .. don't touch it with fingers or arms. This technique also lowers possibility of cracking the ceramics. I usually lay out everything that has to be done in advance with extra planning. Hey, I didn't say it was going to be quick... . Bill Atlanta . . --- In Repeater-Builder@yahoogroups.com, wd8chl wd8...@... wrote: On 8/2/2010 11:15 PM, skipp025 wrote: ... The entire project including obtaining the parts from recycled radios takes me about 4.5 hours with beverage of choice and some decent AM Talk-Radio playing at low back-ground volume level (no, not the right-wing whack job stuff). As opposed to the left-wing whack job stuff? ;cD Once you've had to do this type of Motorola PA repair, you more fully appreciate trying to keep the amplifier happy and cool. Boy, ain't that the truth!!! My only other comment-it's not absolutely mandatory, but if you can get silver solder, use it.
Re: [Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
Bill wrote: Apparently no one here got the moto memo on working with giant heat-sinks. First you only need a 30-40 watt iron to work on them as moto did at the factory The secret is.. raising the heat-sink to about 3-400 degrees while you are working on what needs to be done. PS .. don't touch it with fingers or arms. This technique also lowers possibility of cracking the ceramics. I usually lay out everything that has to be done in advance with extra planning. Hey, I didn't say it was going to be quick... . Bill Atlanta The amplifier in question is a MSR2000 VHF, not UHF - no ceramics to worry about - no oven required. Kevin
[Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
The amplifier in question is a MSR2000 VHF, not UHF - no ceramics to worry about - no oven required. Kevin Don't know what you'd really use the Oven for... For the VHF PA (like the Micor) I switch from the mondo iron to the trusty Weller 550 and 8200 guns. I feel it's better get on and off a section as quick as possible. Weller also makes a decent size iron like the WP-60. s.
RE: [Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
I use the mass of an old martial-aid size soldering iron, which are often passed over by uninformed souls shopping at Ham Flea Markets. s. Skipp, you kill me! They used those in sheet metal shops and doing rain gutters. Got one and it is amazing on touch and ping off it comes!. The solder iron anyway..
RE: [Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
Hmmm my comments were lost. Oh well I just commented you kill me Skipp. _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kevin King Sent: Tuesday, August 03, 2010 2:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How? I use the mass of an old martial-aid size soldering iron, which are often passed over by uninformed souls shopping at Ham Flea Markets. s.
[Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
martinfriedman67 radi...@... wrote: Our Amateur radio club's Motorola MSR 2000 continuous duty amp needs repair. I cant figure out how to remove the amp board from the heat sink. I removed all screws from corners as well as the transistors. It seems to be held by the center, just below the tall air variable cap. I tried heating the solder in the area but, no joy. I don't want to crack the board. The drawings in the manual I found here do not show even the screw holes. Thanks in advance, 73, Marty (WB2BEW) Been there, done that, coffee mug and T-shirt It's not easy... I'm doing two MSR-2000 PA's right now (just in the door yesterday) and I completed my last MSR UHF PA repair a year or two back. Everyone has a different technique and mine depends on the specific failed stage/parts. I use a very large mass soldering iron (better than a gun) to quickly get on and off the portions I need to deal with. I reflow the solder in most of the anchor places using a small amount of new (solder) and lots of quick on/off, well spaced long-time to slowly cool down... between applying the iron to repeat locations. Then comes a decent amount of quick on/off Solder Wick to remove much of the original and added solder, then flat blade X-acto knives (and razors) to carefully wedge up the securing contact surfaces. Sometimes I can and do reflow a bit of solder back into the cleaned section during the flat blade lift process as a method of quickly transferring heat to a very localized area/spot. The key is to get/keep the ceramic substrate as cool as possible. The MSR Power Supply pins poke up into the substrate(s) ... The entire project including obtaining the parts from recycled radios takes me about 4.5 hours with beverage of choice and some decent AM Talk-Radio playing at low back-ground volume level (no, not the right-wing whack job stuff). Once you've had to do this type of Motorola PA repair, you more fully appreciate trying to keep the amplifier happy and cool. cheers, skipp
[Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
radi...@... wrote: OK Kevin, I had already tried the desoldering with a really good Pace unit, but the heat did not transfer well. Yep, not enough heat available from most solder suckers, irons and guns. I will get a buddy to help and use my Weller guns. I have a big 250 watt one here somewhere. Marty The Weller 550D gun is probably the smallest gun you can realistically get away with using. I use the mass of an old martial-aid size soldering iron, which are often passed over by uninformed souls shopping at Ham Flea Markets. s.
Re: [Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?
Maybe a little Black Powder might be needed? Gordon ZL1KL Tauranga N.Z.
