|
Post by n4dxx on May 18, 2019 2:39:34 GMT -5
Picked up a nice s-27/23 combo..worked great for a while and all at once i lost my transmitted audio..I have checked all tubes and they are good..Produces good power.Tried 3 mics and No squeal and No modulation..Thanks for any help
|
|
|
Post by n4dxx on May 19, 2019 12:17:26 GMT -5
Cant find a schematic on this but i found what looks like a Light fuse coming from the 12ax7 tube and it's in series with a 1 megaohm resistor going towards the spot button..anyone here have a schematic they care to share on this transmitter?
|
|
|
Post by 2600 on May 19, 2019 22:00:11 GMT -5
Just got back from the Dayton Hamvention. Don't have that diagram at home, but it should be on file at my shop. I'll post it here when I get back to work.
73
|
|
|
Post by n4dxx on May 20, 2019 7:20:00 GMT -5
Thanks I'll be waiting!!
|
|
|
Post by 2600 on May 21, 2019 12:14:37 GMT -5
Whups! Got an error message. "This forum has exceeded its attachment limit". Can't just attach the file. Here's a copy I posted at ImageShack. With any luck, it will come up at full resolution. 73
|
|
|
Post by 2600 on May 21, 2019 12:17:35 GMT -5
Whups! It only comes across as a shrunken-down version. Not so useful. Maybe this will work better? imagizer.imageshack.com/img923/4326/iFbqkn.jpgYou'll have to click on the image from that page, maybe it will come across at full resolution. 73
|
|
|
Post by 2600 on May 21, 2019 12:23:25 GMT -5
Cool! Worked okay for me. Click on the image to blow it up, then right-click and select "Save image as".
73
|
|
|
Post by n4dxx on May 21, 2019 22:36:14 GMT -5
Thanks..There was a light that was hooked between the 2 10 megaohm resistors was burned black.Shown as L-1 looks like.Can you tell me what type of bulb this is?Thanks
|
|
|
Post by 2600 on May 22, 2019 23:49:33 GMT -5
It's type NE-2, a neon bulb. It serves as a relaxation oscillator, to put an audio tone onto the spot carrier. It goes dark when you key the mike, and only runs from the Spot button.
73
|
|
|
Post by n4dxx on May 23, 2019 0:31:33 GMT -5
Well that tells me thats not my no audio issue..Tested all tubes and it's making good rf but nothing on the audio
|
|
|
Post by n4dxx on May 23, 2019 13:36:00 GMT -5
Well that tells me thats not my no audio issue..Tested all tubes and it's making good rf but nothing on the audio Done some testing,On pin 5 of the 12ax7 it calls for 120v and i am only seeing 6.5 v AC ..I'll admit im not the sharpest tool in the shed on these tube types but i am trying
|
|
|
Post by tubefan on May 23, 2019 13:51:48 GMT -5
Look for an open resistor. Use your ohm meter. Either unplug and discharge then check all resistors. Or with power on check voltage on both sides of resistors. BUT ! remember, there is HIGH voltage. So be sure to look at schematic and see what the voltage on meter should be on for each resistor. AND BE CAREFUL !!
|
|
|
Post by tubefan on May 23, 2019 14:02:23 GMT -5
And of course, start in the audio section.
|
|
|
Post by n4dxx on May 23, 2019 14:08:35 GMT -5
Will do and i am being very careful..Just to be clear this transmitter will modulate without the receiver correct?Or i should ask is there anything in the receiver to stop the audio..But i dont think there is..Correct me if i am wrong
|
|
|
Post by n4dxx on May 23, 2019 14:32:56 GMT -5
And of course, start in the audio section. Well back to square 1..That is pin 6 on the schematic not pin 5 kinda worn..The 6.5 vac is correct on pin 5.Still no audio can't find any blown resistors..Voltage seems to be everywhere it needs to be..Stumped
|
|
|
Post by tubefan on May 23, 2019 14:45:02 GMT -5
Yes, it will modulate without receiver. Does that transmitter have a mic gain pot on the rear? Or on the chassis?
|
|
|
Post by n4dxx on May 23, 2019 14:48:50 GMT -5
on the inside in the middle by the 6bq5 tube..Question on the mic input is that just a standard .001 cap i would assume it is..Thanks for you time on this
|
|
|
Post by tubefan on May 23, 2019 15:04:19 GMT -5
Did you jump it out or check it with a meter? Listening on another radio is it dead silence from that transmitter or is there a loud hum? Also while transmitting and listening on another radio if you move that pot do you hear any static or silence?
|
|
|
Post by tubefan on May 23, 2019 15:06:50 GMT -5
Also, stupid question, but are you sure you are using a known good mic? You can key the radio. Listen on another and touch the audio pin on mic jack with a screw driver. Plastic handle of course and listen for. Buzz or static on other radio
|
|
|
Post by n4dxx on May 23, 2019 16:14:20 GMT -5
Yes i jumped it out as well replaced it..And listning on another radio dead silence ..No hum..I tinkered with the audio gain but heard nothing..I may try that next while transmitting..I have tried the screwdriver thing into the mic jack and no buzz..dead silence
|
|
|
Post by tubefan on May 23, 2019 20:49:53 GMT -5
On some of the older tube transmitters there was a bulb for a modulation light. If the bulb was out it would kill the modulation. Does that transmitter have a bulb for modulation?
|
|
|
Post by tubefan on May 23, 2019 20:51:55 GMT -5
Just looked at schematic up above. How about i3. Is that lit when transmitting?
|
|
|
Post by n4dxx on May 23, 2019 21:37:51 GMT -5
i will check it..Thanks
|
|
|
Post by n4dxx on May 23, 2019 21:45:29 GMT -5
Just looked at schematic up above. How about i3. Is that lit when transmitting? Look at this..Black as can be..That is the audio light on the front of the radio..And it's not lighting up.Reads open.But this may be normal as it uses gas to light the bulb.Anything i can use besides a bulb temporary to see if it will modulate?i will have to order some of these I tried unhooking the spot light neon bulb moving it to the audio..and it just lights for a split sec when i key and unkey.. Attachments:
|
|
|
Post by n4dxx on May 30, 2019 14:38:06 GMT -5
Replaced the neon bulbs still no audio..I am stumped for sure..
|
|
|
Post by tubefan on May 31, 2019 7:30:25 GMT -5
Do you have anything you can use as a tone generator? If you can pump a tone through a .01 cap and follow the schematic down the audio chain feeding the tone while listening on another radio you can maybe find the point of loss. Just a poor mans way of signal tracing if you do not have test equipment. If you checked and tried swapping tubes. Checked all resistors , maybe a bad cap. Have you taken voltage checks all The way down the audio chain?
|
|
|
Post by tubefan on May 31, 2019 7:35:08 GMT -5
Also, when you use the spot button can you hear a tone in the receiver?
|
|
|
Post by n4dxx on Jun 2, 2019 14:44:00 GMT -5
Nope can't hear the tone even after putting in a new NE 2 bulb
|
|
|
Post by n4dxx on Jun 4, 2019 20:49:31 GMT -5
Nope can't hear the tone even after putting in a new NE 2 bulb where you go tubefan..?
|
|
|
Post by tubefan on Jun 4, 2019 21:03:00 GMT -5
I'm here. Do you have something you can use as an audio generator? Even a small battery powered transistor radio. You need to trace the audio and see where you lose it. The audio circuit is only so big in that radio. If you checked all the resistors in the audio circuit from end to end and all the tubes are good and all the voltages are where they should be from the start of the audio chain to the end of the audio chain then I dont think there is much I can help with. I wish I could be the one to give you the magic answer to fix it. But I'm stumped at this point.
|
|