Eagle 2000 ept360014b

[brandon7861]

More times that I rather admit to, I find my hypothesis was wrong, so don't discount Bayou's experience. They did shift some product detector levels around there so he could be onto something. Lets explore both options.

If you have a signal generator with good attenuators, you can see if the radio holds true to the AGC spec in the owners manual. For the DX99V it is listed as less than 10dB change in audio level for input signals ranging from 10uV to 100,000uV. The saturn manual states no more than 12dB change from 10uV to 400,000uV. If we are nowhere close to these specs, the AGC is the place to start. If we still stay within that 10 or 12db audio change, maybe there is something wrong in the product detector. I would expect the radio to sound decent within factory spec.

 

[ira parker]

Sorry for the late reply been tied up with some honey do's. I'm about half way thru the agc circuit nothings jumped out at me yet a few ceramics a little out of spec nothing drastic but replaced them with new ones. tr19 and tr21 were a little low on hfe so I've replaced them. IC 1 voltages look good except pin 10 has 2.3 volts on it and varies with the squelch, I think I have a good one to swap out. What's everyone's thoughts on the pin diodes 15 and 16 I read somewhere that they can test good as a diode but not be responding to the rf changes. The majority say replace them with Iss53 which aren't pin diodes any thoughts on this, I may have a used set of the mc301s. I've got an old rf oscillator put a 27.205 signal with low modulation in and tested it at the d15/16 junction has a clean signal on am but usb was a little dirty and lsb went crazy on the scope I didn't adjust the frequency for ssb modes the old oscillator is to touchy. Another thing I've noticed is the difference between the early board schematic and the late version schematic I believe mine is the late model as it has c33 in it not sure of it. In looking at the copper side parts I've seen 3 or 4 different layouts for this 360014b board, none of them match what I have on mine (no diodes at all not even the surface mount one) it's got the smoothing caps on the pa stage and one to chassis ground and the 2 resistors that's it. Just trying to check anything obvious. I'll post what I find in the next section of the agc in a few days. Thanks Ira

 

[ira parker]

Sorry for the late reply been tied up with some honey do's. I'm about half way thru the agc circuit nothings jumped out at me yet a few ceramics a little out of spec nothing drastic but replaced them with new ones. tr19 and tr21 were a little low on hfe so I've replaced them. IC 1 voltages look good except pin 10 has 2.3 volts on it and varies with the squelch, I think I have a good one to swap out. What's everyone's thoughts on the pin diodes 15 and 16 I read somewhere that they can test good as a diode but not be responding to the rf changes. The majority say replace them with Iss53 which aren't pin diodes any thoughts on this, I may have a used set of the mc301s. I've got an old rf oscillator put a 27.205 signal with low modulation in and tested it at the d15/16 junction has a clean signal on am but usb was a little dirty and lsb went crazy on the scope I didn't adjust the frequency for ssb modes the old oscillator is to touchy. Another thing I've noticed is the difference between the early board schematic and the late version schematic I believe mine is the late model as it has c33 in it not sure of it. In looking at the copper side parts I've seen 3 or 4 different layouts for this 360014b board, none of them match what I have on mine (no diodes at all not even the surface mount one) it's got the smoothing caps on the pa stage and one to chassis ground and the 2 resistors that's it. Just trying to check anything obvious. I'll post what I find in the next section of the agc in a few days. Thanks Ira

OK got the eagle to straighten out. Here goes, went thru the agc circuit completely only found a few items out of spec replaced them as I went, got to D-10 still had severe distortion with full rf gain so I removed everything in circuit to isolate it. Still had distortion, so it had to be coming in on the ground side, did some testing back to the power supply sure enough that's where it was sourcing from so I removed it from the board and used an external supply wooohooo no distortion. So the old under rated iron core went to the circular file and installed a nice 36 amp switcher, a little over kill but should last forever. Once again Thanks for everyone's help and I hope if anyone has a similar problem this solution will help. Thanks Ira