Midland 13-898B Low SSB Power Out

[Justin B.]

I was tied up all yesterday and most of today but I'll try to get some scope grabs later today. You are wanting to look at the RF out at the antenna connector, right? AM or SSB or both?

73,

 

[nomadradio]

Yeah, that's the starting point to look for flat-topped modulation peaks.

73

 

[Justin B.]

Here are the AM scope grabs:

Dead key-


With a yell-


LSB dead key-


LSB yell-



73,

 

[Justin B.]

Brandon - Here is the AGC signal, with a yell, at C306:



I checked the preamp out signal and the AGC signal on the "good" radio and it was considerably different...

73,

 

[brandon7861]

Brandon - Here is the AGC signal, with a yell, at C306:

View attachment 77481

I checked the preamp out signal and the AGC signal on the "good" radio and it was considerably different...

73,

C306 is after the diode detector, we should not have AC appearing here.

Are you sure you were not probing C310's cathode? That would look just like the waveform you shared.

 

[Justin B.]

Brandon - I'll try to re-check these tomorrow. Had too much stuff going on today and never made it out to the shop! Been working on the car and bike...

 

[Justin B.]

I verified that C306 has a 100 uf cap installed. Here are some scope grabs around IC301.

D301 Anode:


D301 Cathode:


IC301 pin 2:


IC301 pin 6:


Negative side of C309:


D301 cathode and IC301 pin2 look strangely familiar...

73,