View Full Version : PA Modules

01-16-2008, 02:25 AM
just a side note
thank you

my PA Module in my ic 2100-H went south, the pre drive is fine
i have also stumbled across another pa here in the shack
i found out the info as follows:

S-AV6 Description for RF Power Module:

Parameter: Value:
S-AV6 Vendor: Toshiba
Package Dimensions: 5-53P
Output Power Po (W): 28
Input Power Pi (W): 0.2
Frequency Range: 144 to 162mc
Vcc (V): 12.5/12.5
Application(s): VHF Marine

the PA in the ic 2100 is as follows:
Icom SC1091

but i can't find out any data on the icom SC1091 like i did on the Toshiba S-AV6

any help?

01-16-2008, 03:19 AM
This site;


has this to say;


ICOM 50W VHF Units

* The most common symptom is low or no Tx power. This is usually caused by the VHF Power Amp. This is not ICOM's fault so much. The SC1091 is the 45/50 W final Module, and has the generic name of SAV17. The SAV17 has a weak design, the transistor mounting is too close to the ceramic PCB the compontents are mounted to, and as the transisitors heat they push on the ceramic surface, sometimes the pressure is to extreme and the surface cracks breaking the VCC power to the final or driver. This is usually repairable. Not always though. Low power setting is not any better and actually may be worse, the module is biased for 50W operation and low power is very inefficient, so there is still allot of heat release to the heatsink.


The S-AV17 data sheet is here;

http://www.datasheetarchive.com/search.....sub.y=0 (http://www.datasheetarchive.com/search.php?t=0&q=s-av17&manystr=&sub.x=0&sub.y=0)

01-16-2008, 03:26 AM
Toshiba is a manufacture of RF transistors, power transistors, and power modules. ICOM manufactures radios and buy their power modules from whomever. The number on your module is probably a ICOM "in house number" which the manufacture of the module is more than happy to print on the power module as long as you buy 100 thousand of them. ICOM gets a big profit in suppling replacement parts since they are the only game in town.

See if The Toshiba "pinout" is the same as the module that failed. There are only two our three big time module manufactures.

73, Good luck


01-16-2008, 04:10 AM
There are several modules that could work as a replacement for the SAV17, depending on what you want for power out. Some of them might require slight modification of the input power, by adding a pad, and also reduction of the control voltage.

The SAV6 could work, but you would have lower power out, and lower efficiency, since it is spec'd at about 8MHz higher in freq. You would also need to pad the input power by about 3dB, and you would end up with 30 watts or less out.


01-16-2008, 05:36 AM
i had an alinco DR 605 that the vhf module went south, i dumped the radio as the cheapest i could get a module was $69 plus shipping, not worth the trouble for me as i got the radio free, you can get a replacement module, search google for the info, hope its worth the money.

01-16-2008, 05:49 AM
Looks like the SAV-17 is the correct replacement part, and the SAV-6 is pretty far off. if you really want some semblance of original operation and reliability, it's better to stick with the original part.

R.F. Parts (San Marcos, CA) usually has the replacements in stock; you can contact them and they can give you some informed advice as to an acceptable replacement for the Icom part number. (And have a much lower $ than the part from Icom.)

If the SAV-17 has a reliablility problem, than that is the fault of Toshiba, although Icom is partly to blame for using a part that performs poorly. Toshiba apparently has a replacement part; R.F. Parts should be able to advise you on the matter. I have dealt with them before, and always been more than satisfied. (They have, in fact, gone out of their way more than once to accomodate an unusual request.)


Also look at the voltage rating. If your figure for the SAV-6 is correct: a max. of 12.5 Volts; the SAV-17 has a max. voltage rating of 16 Volts, MUCH more appropriate for a mobile radio that's designed to operate from a nominal 13.8 Volt supply, or even higher in a mobile environment.

As they say, "Choose wisely."

01-16-2008, 06:38 AM
The SAV6 and 17 are similar devices, voltage wise. The 6 requires less input power, and puts out less output power. It is also spec'd at 154-162.

It will probably work OK at 2M, with reduced output.

I think one would work OK in that radio, if a person didn't want to shell out the $50+ for the 17, and already had a SAV6 on hand.

Adding a 3dB pad to the input should fix the input level, then adjust the max output to 25 watts or less.

A cheap fix if you wanted to do that, but not the best.

The SAV32 could also easily be modded to work, it is only $45, and puts out over 50 watts.


01-16-2008, 06:43 AM
this might help you, it didn't help me but worth a try,
also the sav 24 is listed as the same spec as the sav17 at rfparts, its a heafty $90 though. could try this one, looks compatable, look at the spec at http://www.ortodoxism.ro/datashe....vtq.pdf (http://www.ortodoxism.ro/datasheets/MitsubishiElectricCorporation/mXuyvtq.pdf)

listed as $59

01-16-2008, 03:50 PM
One final comment. Make sure that the series "Pin Diode" in the transmitter T/R switch didn't fail. I've seen more failed diodes than power modules in 2 meter rigs. The diodes usually fail when the rig is operated with a 1/4 wave whip antenna (no DC ground or static bleed off resistor installed) and gets zapped by static buildup on the antenna.

Good Luck,


01-16-2008, 09:14 PM
hi all,
and tnx for the posting's

I still need to know if the pin outs are the same for each module so they don't cross or anything, in other words are they pin for pin so i could take out the Sc1091 module unit, and replace it with the Toshiba S-AV6 module, pin for pin and also turn down the pre drive for a total of 25 w output?
do i understand this correctly ?

BTW- pin diode tests ok

many tnx

01-16-2008, 09:35 PM
ICOM part is unknown. However, if SVD is correct and a SAV17 is the replacement part then the SAV6 has the same pin out as the SAV17.

EDIT: Caution SAV6 has a 300 mW maximum input power rating.

01-16-2008, 11:25 PM
heres the scope
checked D7 pin diode, was testing ok WAS!
installed the Sav 6 set pre drive to 250mw
still no output?

scraching my head...
i connected a test lead before the diode in to a test watt meter, set the radio to low pwr setting, booom 5 watts out
this lead me to testing the diode again this time i got nadda
i lifted one side of D7 and tested it again set my D/v/ohm meter to diode Test --->|---, still nodda, checked
the reverse --|<-- and still nodda
so this this point all is good, i think, just a bad Diode i think and even may be the Sc1091 is ok too maybe

now for my next question
I have not played about with the inside of a radio for many years but still able to do the simplest checks lol anyhow

what can i replace D7 with? i dont have a service manual here and i did a quick google serach for the IC2100-h service manual but got a bunch of broken links...

there are no markings on the D7 Diode's glass just a balck band indicating the Cathode A -->|-- C even had it under the mag light... no luck...
any advice?
tnx for all the help...

01-16-2008, 11:47 PM
I would get a service manual for the rig. Try KB2LJJ's site.

As far as the module goes...eBay's yer buddy. Those things were used in lots of Kenwood's TM2xx-series radios, and it's the displays which usually fail on those rigs. Ergo, you might be able to get a parts rig cheap.

01-17-2008, 01:26 AM
well today i guess is a good day
i replaced the pin diode with a 31v zener with hi rev. bias BINGO
25 watts, i also reinstalled the old SC1091 re-did the pre drive BINGO 55 watts

so all isw well again
thank you all for all of the inputs
7 3 to all

01-17-2008, 03:16 AM
I would still get a new pin diode.

01-17-2008, 03:16 AM
Quote[/b] (k4eez @ Jan. 16 2008,18:26)]well today i guess is a good day
i replaced the pin diode with a 31v zener with hi rev. bias BINGO
25 watts, i also reinstalled the old SC1091 re-did the pre drive BINGO 55 watts

so all isw well again
thank you all for all of the inputs
7 3 to all
I'd still recommend replacing the diode with the proper type when you get a chance.

01-17-2008, 03:18 AM
Echo in the room!

01-17-2008, 03:31 AM
Quote[/b] (K7JEM @ Jan. 16 2008,20:18)]Echo in the room!

Echo or "stereo?"
Looks like we posted at the same time.:D

But it's good advice. probably at least improve reception and better protect the receiver.
Hope he reads and heeds the advice.

01-17-2008, 03:59 PM
Quote[/b] (AC0FP @ Jan. 16 2008,08:50)]One final comment. Make sure that the series "Pin Diode" in the transmitter T/R switch didn't fail. I've seen more failed diodes than power modules in 2 meter rigs. The diodes usually fail when the rig is operated with a 1/4 wave whip antenna (no DC ground or static bleed off resistor installed) and gets zapped by static buildup on the antenna.

Good Luck,

I've had experience with this. Try getting a UM9401 PIN diode. why, ordinary diodes will fail after awhile and they do not have the necessary reverse isolation to decouple the transmitter from the receiver. This may cause loss of receiver sensitivity due to the XMTR circuit now being part of the receiver matching network.

Try this link for the diode data sheet, this diode is the one usually used by transceiver manufactures.



Frank http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

01-17-2008, 09:42 PM

This may sound like a stupid questions to ask about Pin diodes

testing a pin diode with a v/ohm meter do you test it in the same manor like any other diode, or would one need to apply more than .5v to switch the diode state so in other words do you need to apply Fwd voltage thru the diode {A to C}for it to change state so it switches on and passes Fwd Voltage.

also when a pin diode decides to go south still in the ckt. where dose all that RF go? just sits there doing nothing on the ckt or ?

tnx for the link to the pin diode web site, i was just reading the pdf file and just thought i would ask


01-17-2008, 11:23 PM
The diodes fail open usually, therefore they look like an open circuit to the PA device. VSWR is very high, with what power that is developed being reflected back into the PA device.

PIN diodes test with a DC ohmmeter just like any other diode, it their RF behavior thats different. When forward biased with a comparatively small DC current they can pass a RF signal linearly and their RF impedance is a very low < 1 ohm. When turned off they exhibit very high impedance and low shunt capacitance across the diode junction.



01-18-2008, 08:48 PM
thank you for clarifying the Pin diode and thank you for all the advise from the other hams
Very 73 good work http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

05-24-2009, 01:44 AM
just bought a "hamfest special". of course he told me worked FB but when got home it didnt put out over 9W. low power was around 7W and i did all the voltage checks. the module seemed to be OK, popped off the cover and nothing unusual found. desoldered one leg of the pin diode (D5 in this case) and diode seemed to be OK but when i jumped the SC-1091 output to the output it worked as it should have all along. its obviously that damn PIN DIODE trying to fool me.

only issue is i see RF parts may be the only way i know of to get another one of these (like the UM9401 mentioned above). NTE doesnt show any cross references- how crazy huh?

anyone else have some ideas?
would a good ol 1N4003 work in there?


05-24-2009, 04:21 AM
Just another approach - but if the diode part is unknown or unreadable, I usually find other circuits in the same equipment use the same parts.

Manufacturers tend to do that by default - so while one diode may not be readable, another one in the equipment might be perfectly readable...

I usually run into having to do that when I encounter the charred remains of some part inside radio equipment that I can't locate a schematic for. (Yup, we have no trouble finding the dead sea scrolls - but no schematic for a modern day radio though...)

You know the radios - , these are usually family members (and their friends) who pawn off some unknown radio equipment no one has ever heard of before that must have been manufactured by an alien civilization on another planet. In addition, I can only suspect the internal charring I find inside on the internal circuitry occurred due to re-entry into the earth's atmosphere, because it's apparent none of my family members ever seem to have any idea how the radio "blew up" in the first place!?

So, I just "mind meld" with the various circuits inside without a schematic to find out what went wrong. I usually find many parts especially diodes are repeated in the circuitry in many instances. Sometimes you have to "logic it out" by taking measurements and comparing datasheet ratings of other components used in the same circuit to determine appropriate replacement parts in some cases. Perhaps that approach will help if you run across something without a schematic in the future. :)