I am working on a UHF MSR2000 and have an issue with the PA. The three finals have gone south - the driver output has 45 watts, the finals together have 40 but if you unsolder each one separately the output drops to 10 watts. I was wondering if I could just bypass the three finals feeding the driver to the harmonic filter then using an external amp (20w in, 100w out). This repeater also has a low level amp board that is different from the one in the documentation that is on the Repeater Builder site. The part number is TLE5791A. This has only one transistor as opposed to the two transistor unit, part number HLE4060A. Does anyone know of a schematic available somewhere for this board other than /\/\? I hand drew one but wanted one with voltages and such. Other readings on this repeater are: approx 1 watt out of the exciter, about 8 watts out of the low level amp and 45 watts out of the driver. 15.3 volts out of the supply which drops to 14.5 as the unit is now. The power control does work as does the current limit circuitry. Thanks in advance for assistance....
Neal KC4YCM
MSR2000 UHF question and predriver help
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Re: MSR2000 UHF question and predriver help
One problem with those is the DC power feed board under the PA. Some of the solder joints go bad due to heating and then cooling.
Re: MSR2000 UHF question and predriver help
Every MSR2000 I placed at sites has had a 24 VDC requirement, even the backup batteries were wired to supply 24 Volts.
Re: MSR2000 UHF question and predriver help
@ Will - there is definately + 15 volts at the finals. I triple checked for cold solder joints and fried resistors & chokes.
@ AEC - The supply is + 15.8 volts. This is a UHF unit. There are no connections on the power supply that I can see for backup battery. The PDF on another site says the standard high current supply output is between 13.1 (36 amp draw) & 16.3 volts (2 amp draw) with 30.1 amp draw w/14.1 volts. The supply is intact and shows no visible evidence of anything fried. When the amplifier is on, the supply voltage drops from 15.8 volts to 14.5 volts. Another item that has me scratching my head is the schematic for the PA shows the finals to be bipolar NPN transistors but the driver and finals are M2502 which cross to MOSFET transistors. I know that a MOSFET can be substituted for a bipolar if you change a few parts but nothing appears to be modified in this PA>
@ AEC - The supply is + 15.8 volts. This is a UHF unit. There are no connections on the power supply that I can see for backup battery. The PDF on another site says the standard high current supply output is between 13.1 (36 amp draw) & 16.3 volts (2 amp draw) with 30.1 amp draw w/14.1 volts. The supply is intact and shows no visible evidence of anything fried. When the amplifier is on, the supply voltage drops from 15.8 volts to 14.5 volts. Another item that has me scratching my head is the schematic for the PA shows the finals to be bipolar NPN transistors but the driver and finals are M2502 which cross to MOSFET transistors. I know that a MOSFET can be substituted for a bipolar if you change a few parts but nothing appears to be modified in this PA>
Re: MSR2000 UHF question and predriver help
@ Will - I checked for cold solder joints on all the boards and the power control. All the voltages are within specs. I also checked for fried resistors/coils and shorted caps.
@ AEC - The manuals I have for the repeater and power supply both say 13.8 - 15 volts. The power supply has a 9.4, 14 & high current outputs with the high current being 13.1 volts (36 amp load) to 16.3 volts (2 amp load) and 14.1 volts w/30.4 amp load.
@ AEC - The manuals I have for the repeater and power supply both say 13.8 - 15 volts. The power supply has a 9.4, 14 & high current outputs with the high current being 13.1 volts (36 amp load) to 16.3 volts (2 amp load) and 14.1 volts w/30.4 amp load.
Re: MSR2000 UHF question and predriver help
Not true, the UHF are 15 volts feroresonate transformer powered. The battery back is 12 volts with a different power supply.AEC wrote:Every MSR2000 I placed at sites has had a 24 VDC requirement,
Re: MSR2000 UHF question and predriver help
For those interested in the outcome of this project, here is what I have done:
I raised the power feeders for the three finals (the ones with the ferrite
beads) in case someone later decides to spend the bucks to replace them. I also
raised the jumper between the final divider that feeds the finals and the center
of the coax that is fed from the capacitor on the output of the combiner for
the finals. I used a piece of rigid 50 ohm coax to jumper from the driver
output coupling capacitor and the coax center conductor that feeds the harmonic
filter. I grounded each end of the rigid coax and left all the jumpers
connected to the final board, again in case someone wants to replace the finals.
The rigid coax is CF141-50. It can handle 3.5 KW and has a bandwidth of 30 MHz to 18 GHz. I now have
45 watts full power out of the repeater power amp. The power adjustment pots
have been reset to reflect the changes. The actual power output will be set at
10 watts to drive a Henry 100 watt continuous duty amplifier that requires 10
watts drive. I did some checking with Henry and found that the transistors that
are used have a maximum CEO voltage of 16 volts. As long as the output power
does not go over 100 watts then the transistors 'should' operate normally. The
existing power supply (15 volts) is powering the amplifier as well. With the
original finals disconnected, the power supply has plenty of juice to run the
Henry unit. I talked with the repeater owner and he is happy with the power
being set at 90 watts (to further guard against any transistor issues). The
unit is cooking in my basement until it can be put back in service in a few
weeks.
Neal KC4YCM
I raised the power feeders for the three finals (the ones with the ferrite
beads) in case someone later decides to spend the bucks to replace them. I also
raised the jumper between the final divider that feeds the finals and the center
of the coax that is fed from the capacitor on the output of the combiner for
the finals. I used a piece of rigid 50 ohm coax to jumper from the driver
output coupling capacitor and the coax center conductor that feeds the harmonic
filter. I grounded each end of the rigid coax and left all the jumpers
connected to the final board, again in case someone wants to replace the finals.
The rigid coax is CF141-50. It can handle 3.5 KW and has a bandwidth of 30 MHz to 18 GHz. I now have
45 watts full power out of the repeater power amp. The power adjustment pots
have been reset to reflect the changes. The actual power output will be set at
10 watts to drive a Henry 100 watt continuous duty amplifier that requires 10
watts drive. I did some checking with Henry and found that the transistors that
are used have a maximum CEO voltage of 16 volts. As long as the output power
does not go over 100 watts then the transistors 'should' operate normally. The
existing power supply (15 volts) is powering the amplifier as well. With the
original finals disconnected, the power supply has plenty of juice to run the
Henry unit. I talked with the repeater owner and he is happy with the power
being set at 90 watts (to further guard against any transistor issues). The
unit is cooking in my basement until it can be put back in service in a few
weeks.
Neal KC4YCM