Motorola S1327 Service Monitor Schematic

[re1091]

Hello,
I have acquired 2 Motorola S1327B Station Monitors that are not working. The lock lights come on but I cannot monitor TX or generate RF. Does anyone know where I could get an Operators Manual or Schematic?

Thx
Richard

[DJP126]

Hello Richard, welcome to batlabs. The S1327 has only one lock light (next to the thumbwheels) and it should be steady, not flashing. If the monitor is locked, check the connection between the RF board and the coax relay (I suspect a bad jack or a bad connecter). the relay routes the output of the RF board to the attenuator (for generator output) or to the mixer module (top center plug-in, for monitor mode). Also, the generator output uses two 1/10th amp fuses on the output, both must be good.

[re1091]

Dave,

Thanks for your guidance. It looks like 2 of the 1/10 amp fuses are blown and one of the cables was not seated in the relay that you directed me to. I wanted to ask you what the advantage is in using the 145-175 preselector rather than the broadband mixer. What are the voltages on the PS board that slides in the bottom at the test points? Does the preseletor have more gain or selectivity? One of the units seems to be working now. Do you know where I could get a schematic? Thanks so much for sharing your knowledge.

Regards,

Richard

[GlennD]

The 1327 has so much phase noise that anything but an early Cushman is better. Motorola had to practice until they got it right. the 2001D series is so much better. Even the 1200 is better.

[DJP126]

Dave,

Thanks for your guidance. It looks like 2 of the 1/10 amp fuses are blown and one of the cables was not seated in the relay that you directed me to. I wanted to ask you what the advantage is in using the 145-175 preselector rather than the broadband mixer. What are the voltages on the PS board that slides in the bottom at the test points? Does the preseletor have more gain or selectivity? One of the units seems to be working now. Do you know where I could get a schematic? Thanks so much for sharing your knowledge.

Regards,

Richard

The power supply voltages are +5, -5.2, +15 and -15 VDC. I don't remember which test point is for which voltage. The preselector has MUCH better sensitivity than the broadband mixer. IIRC the specs on the broadband mixer was 5mV versus 20 uV for the preselector.

GlennD, you are correct about the S1327 series output being noisy, but don't blame Motorola for that. It was designed and built by Systron=Donner. They also built the R-1200 series which (when properly aligned and calibrated) had the CLEANEST RF output ever. It was even cleaner than ANY of the equipment designed as general purpose since then including Motorola, General Dynamics, HP, Aligent, Fluke or IFR (sorry Wowbagger). An output of 0dBm RF, when looked at on a spectrum analyzer, showed the carrier frequency and the first harmonic. If you saw any spurs of any considerable amplitude, you had an alignment problem. If it wasn't such a heavy beast, I think it would have been liked even more.

[re1091]

Dave,

Do you know where I could get some LF 1/10 amp fuses? .5 amp are the smallest I have been able to locate. It looks like my last issue with the second unit is hum on my -15v power supply more of a sawtooth on my scope. I know the problem is in the power board. Do you have any pointers where to look? The regulator does still regulate. I have replaced two .2ufd black square caps but nothing has changed. Any thoughts?

[DJP126]

Not really sure where you will find the 1/10th amp fuses but I do know that they were manufactured by Littlfuse. As for the ripple on the -15V supply, possibly the large filter cap (mounted above the regulator board) or the pass transistor (mounted on a heatsink which is mounted on the rear chassis). Final possibility is the regulator IC itself (even though it regulates it could still be bad). IIRC they were LM320 chips.

Good luck.

[Andy Corbin]

Dave,

Do you know where I could get some LF 1/10 amp fuses? .5 amp are the smallest I have been able to locate. It looks like my last issue with the second unit is hum on my -15v power supply more of a sawtooth on my scope. I know the problem is in the power board. Do you have any pointers where to look? The regulator does still regulate. I have replaced two .2ufd black square caps but nothing has changed. Any thoughts?

I am not certain what style fuse case you need, but you can go to Ebay and do a search on "pico fuse". There are some low amperage fuses there. Pico fuses are the ones that look like 1/8 watt resistors.

Andy

[DJP126]

Dave,

Do you know where I could get some LF 1/10 amp fuses? .5 amp are the smallest I have been able to locate. It looks like my last issue with the second unit is hum on my -15v power supply more of a sawtooth on my scope. I know the problem is in the power board. Do you have any pointers where to look? The regulator does still regulate. I have replaced two .2ufd black square caps but nothing has changed. Any thoughts?

I am not certain what style fuse case you need, but you can go to Ebay and do a search on "pico fuse". There are some low amperage fuses there. Pico fuses are the ones that look like 1/8 watt resistors.

Andy

I did a search at littelfuse. Unfortunately the fuse they made is obsolete and NLA. Physically it had a small plastic body with radial leads about 1/8th" to 3/16th" apart. A "pico fuse" having axial leads won't work unless you mosify the output assembly.

[Andy Corbin]

Dave,

Do you know where I could get some LF 1/10 amp fuses? .5 amp are the smallest I have been able to locate. It looks like my last issue with the second unit is hum on my -15v power supply more of a sawtooth on my scope. I know the problem is in the power board. Do you have any pointers where to look? The regulator does still regulate. I have replaced two .2ufd black square caps but nothing has changed. Any thoughts?

I just ran across this on Ebay. Could these be what you are looking for?

http://www.ebay.com/itm/Littelfuse-Trac ... 2a34887b61

Andy

[DJP126]

I just ran across this on Ebay. Could these be what you are looking for?

http://www.ebay.com/itm/Littelfuse-Trac ... 2a34887b61

Andy

That's it!