stryker 447 no white noise

[johnecashflo]

good day all, was hoping someone could help me with a problem im trying to fix on a older stryker 447 hpc the big chasis version..my problem is that the speaker jacks act if the are dead but I can hear my talkback and the pa jack also works..just have absolutely no white noise from receive.. I know the receiver section is working right as I can see the meter climbing as I increase the power from my signal generator.. no sound at all for receive. rf gain and squelch and volume pots have all been ohmed out and are working.. also changed audio chip with new one..still nothing.. im not the best with schematics so if someone would be kind enough to look at the 447 schematic and possibly point me in the right direction I would be very thankful.

 

[Shadetree Mechanic]

Speaker jack dead? But you can hear tailback in the radios speaker? Sounds strange, but I have heard of speaker jack problems that will keep the main speaker from working. If the PA works then I would assume that the transmit audio works? Can you confirm this? The meter works on receive, and I believe it uses the same audio circuit as the MIC audio. One thing to check is the mode switch for the AM, FM, PA. Do you get any receive on FM? If the PA switch is bad, it is possible that it won't fully make contact in the receive mode. Hope this helps, I am sure that someone more familiar with the radio will come along.

I have a Stryker 440 and it is a talker for sure.
Chris

 

[Handy Andy]

Lots of times the "speaker" isn't the real problem, the wiring harness to the front panel can cause "intermittent" audio - whiel you have the radio on, pres down on he wiring harness to the front panel - there are several that leave the board from the front.

The audio chip is on a board, bolted to the side of the main panel by the AM Regulator.

The talkback, since you have it, may be caused by someone swapping a header from the front panel - which the speaker routes FROM (not to - the audio chip SENDS to the front panel) - using the front panel PA switch and RX side - when you have no receive - and Squelch seems to work - would also route to here, thru the volume control and SQUELCH board - check that header from the front panel - this sounds like someone may have swapped headers in error.

Now it is also to note that the AGE of the radio - the Squelch control can engage because of the SENSE cap - being C32 by IC1 that "quad op amp" that is the heart of all of this - if its' gone bad, the squelch would "engage" all the time.

If you can....Go here...
http://www.cbtricks.com/radios/stryker/index.htm

The 447 and 497 are similar, only the '97 is using the big-pill final - 2290/2879/1446 depending on year and how many times in the shop...

 

[nomadradio]

Bad volume control? They get banged into the occasional knee in mobile use.

Can't remember what has to be done to reach the three lugs where the volume control connects to the wiring harness in this model.

Laying one finger along the shaft of a thin screwdriver gets you a "hum probe". Touch it to the three lugs of the volume control, one then the next. With the volume control all the way up you should hear a hum in the speaker on the center lug and one other.

Both.

If you hear it on only the center lug alone, the control is probably bad.

73