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I just aquired a very large Motorola 6 meter rig that I need help with. The only model # I can find is 891 rcb-14068 sp2.That # is on the cabinet that holds the amplifier(400 watts) the power supply and seperate transmitter and receiver.I did a google search and found nothing.The rig is crystal controlled so my first question is what freq crystal do I need? One solution would be to by-pass the transmitter and receiver and use a 6 meter transceiver with VFO. Any help would be greatly appreciated. TNX.

Hello Dan!

Please allow me to say hello. My name is Rod.

I recently acquired this unit, and would really appreciate your input on subject: The following information is offered:

B91RCB1406BSP2

From repeater-builder site, this numbering is decoded as being a Base station, 9:Over 260W, 1:25-54MHz, RCB:120V, 1:Carrier Squelch, 4:narrow w/EXTENDER, 0:T1R1, 6:Tone Remote, B:Major Version, SP2: 2 receiver(?) variation.

It is believed that there are indeed TWO receivers. There is a rotary switch on a panel where mic. attaches that has +/- REC.1 , +/- REC.2. +/- PA. I'm thinking these are for tuning the receivers. Not TOTALLY sure this unit has the onboard tuning feature just yet. At TOP of rig, THREE meters appear, one is labeled "TUNING", PLATE VOLTAGE, PLATE CURRENT. The last two are obvious, the first is not quite so obvious yet.

You requested two pieces of information:
CHANNEL ELEMENT FREQ.:
On receiver PCB, there is a number stamped: TLB68-4B1. It is believed the dash (-) is to bridge a solder joint for getting the "real" number, which I believe is TLB684B1. I could be wrong, of course. So, the number FOUR corresponding to "FOURTH" channel grouping # HH: 42-50 MHz ??

Second number on Rx PWB......second section:
THE SECOND number on the receiver deck, located on PWB--second "section"-- is TRN6007A2. Wondering if THIS is the second receiver alluded to by rotary switch?

REMOTE CARD CAGE modules present:
Four Freq.,
Guard Tone Decoder,
F1 PL,
Line Driver,
Station Control,
and Time-Out Timer.

ANY input from you is MOST appreciated,

Thanks,
Rod.

WA9WVX wrote:B91RCB1406A-SP2

MOTOROLA MICOR 1/4 KW 330 Watts Output Low Band VHF Base Station 5 Foot Upright Black & White Cabinet Uses 2135 Key for Door Locks Front & Rear Doors can be removed for Service Work Carrier Squelch with a Receiver Extender Option (Similar to a Noise Blanker) 2-Wire Tone Remote Control High Power RF Amplifier uses a Pair of 8560AS Conduction Cooled Vacuum Tubes RF Drive for P.A. is 6 to 8 Watts Maximum High Voltage should be 1700 VDC at 335 Milliamperes DC Input when tuned correctly Receiver Sensitivity .25 uv at 20 dB Quieting Both the Transmitter & Receiver require separate Channel Elements

Not sure what the SP2 modification is, could be a 2 Receiver Station?

You must supply Channel Element Frequency to know what Frequency Range the station was built for.

Also supply which modules were included in the Remote Card Cage.

73,

Dan

Hi Rod,

Presently I can't access my Micor Low Band Base Station Service Manual because of a health problem. Perhaps the week of June 12 th I'll be able to get to the manual in my basement but I found my Silver Book for Parts and High Level Kit Assembly Numbers.

You will probably have to dismantle certain parts of the station to locate the kit numbers. All of the Low Band Stations were broken down into Four Frequency Ranges.

On the High Power RF Amplifier, here are Kit & Frequency Ranges:

TLB-8141A 25-30 MHz Ideal for 10 Meter Use
TLB-8142A 30-36 MHz
TLB-8143A 36-42 MHz
TLB-8144A 42-50 MHz Modify Up to 6 Meters

For the Receiver RF / I.F. Boards:

TLB-6841B 25-30 MHz
TLB-6842B 30-36 MHz
TLB-6843B 36-42 MHz
TLB-6844B 42-50 MHz

The TRN-6007A is the Audio / Squelch Board for the Receivers.

Since your station has two Receivers, the customers application might have required a Wide Frequency Spacing to maintain the Receiver Sensitivity.

I need to access my manual for other informstion that you'll want or need..

BTW, the 8560AS RF Vacuum Tubes are nothing more than 4CX250B but Conduction Cooled Tubes. Stay away from the Peoples Republic of China 8560AS or MOTOROLA Part # 65-833D02, THEY ARE JUNK! The Russian 8560AS are Good and the Eimac 8560AS ARE the BEST!

73,

Dan