Can some one direct me in the direction of a President washington Service manual... or just the parts lay out...
The radio is a 858pll radio
The radio is a 858pll radio
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President washington service manual
- Thread starter gogo_gadgit
- Start date
http://www.worldwidedx.com/cb-radio...-realistic-navaho-trc-458-service-manual.html
Since it is an 858 chassis, this service manual will get you through the alignments.
Since it is an 858 chassis, this service manual will get you through the alignments.
except for the part where it tells you to bias the final transistor at 15mA.
i have the SAMS for the 858 washington here and the final should be biased at 70mA.
everything else is correct as far as i can tell.
i have had a few discussions about this exact issue, stemming from the fact that the SAMS for the realistic 858 SSB radios shows a final bias of 15mA, and every other manufacturer of 858 SSB radios shows 70mA.
one guy sounded very sure that it should be 15mA on all versions of this chassis, but it turns out he was wrong.
someone VERY knowledgeable about electronics did a test using a scope and the output at 15mA was distorted.
turning it up to 70mA cleared it up nicely.
hope this helps,
LC
i have the SAMS for the 858 washington here and the final should be biased at 70mA.
everything else is correct as far as i can tell.
i have had a few discussions about this exact issue, stemming from the fact that the SAMS for the realistic 858 SSB radios shows a final bias of 15mA, and every other manufacturer of 858 SSB radios shows 70mA.
one guy sounded very sure that it should be 15mA on all versions of this chassis, but it turns out he was wrong.
someone VERY knowledgeable about electronics did a test using a scope and the output at 15mA was distorted.
turning it up to 70mA cleared it up nicely.
hope this helps,
LC
In its infinite wisdom, Radio shack specified some component differences in their 858 chassis radios compared to the ones from other marketers. I have no clue as to why. However, because of these differences, the bias for the final on the TRC 449, 457, & 458 should be set at 15ma. All others should be set at 70ma.
Check out the actual Realistic service manual for the TRC449 on CBTricks site
http://www.cbtricks.com/radios/realistic/trc_449/graphics/realistic_trc_449_sm.pdf
73s.
- 399
Check out the actual Realistic service manual for the TRC449 on CBTricks site
http://www.cbtricks.com/radios/realistic/trc_449/graphics/realistic_trc_449_sm.pdf
73s.
- 399
thanks for jumping in here 399, havent talked to you in a while.
hope all is well with your family.
here is the thread that i was referring to earlier:
Login
for some reason cbtricks is not accepting new members right now, but i think most of you are already members over there.
So 399, after reading through that thread, would you be willing to do the tests that either Sue or Nomad posted on a realistic 858 ssb radio?
i think it would really help to find out if the realistics did indeed perform correctly at 15mA.
LC
hope all is well with your family.
here is the thread that i was referring to earlier:
Login
for some reason cbtricks is not accepting new members right now, but i think most of you are already members over there.
So 399, after reading through that thread, would you be willing to do the tests that either Sue or Nomad posted on a realistic 858 ssb radio?
i think it would really help to find out if the realistics did indeed perform correctly at 15mA.
LC
LC -
Thanks for the shout out. Everything down here is A+, as always. I hope everything on your end is going well too.
That's an interesting thread on CBT. Her textbook explanation of bias settings is technically correct. However, after reading the Cobra service bulletin referred to in the thread, I believe now I understand why the driver/final circuit schematics (and the bias settings) were different on the Realistic 858s compared to the others. The Cobra 139XLR is in Sams # 127. and the 138XLR is in Sams # 126. These were published before the service bulletin change, and specified a final bias of 70ma. The TRC457/458 is in Sams # 207, which was published a few months after the service bulletin, and reflected the revised driver/final circuit, and the new 15ma bias setting. BTW, this service bulletin is shown on page 5 of Sams # 135
So ... I guess what this means is that we need to start looking at the production numbers. But in most cases 15ma will be correct for ALL 858s.
73s my friend.
- 399
Thanks for the shout out. Everything down here is A+, as always. I hope everything on your end is going well too.
That's an interesting thread on CBT. Her textbook explanation of bias settings is technically correct. However, after reading the Cobra service bulletin referred to in the thread, I believe now I understand why the driver/final circuit schematics (and the bias settings) were different on the Realistic 858s compared to the others. The Cobra 139XLR is in Sams # 127. and the 138XLR is in Sams # 126. These were published before the service bulletin change, and specified a final bias of 70ma. The TRC457/458 is in Sams # 207, which was published a few months after the service bulletin, and reflected the revised driver/final circuit, and the new 15ma bias setting. BTW, this service bulletin is shown on page 5 of Sams # 135
So ... I guess what this means is that we need to start looking at the production numbers. But in most cases 15ma will be correct for ALL 858s.
73s my friend.
- 399
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