When I compare the SSB audio quality between my Icom 735 and my TS850, the TS850 seems more susceptible to noise. The 735 just sounds better and seems to reject the noise more. The audio tone is turned down on the 735 but there just seems like there is much more noise on the TS850 for that to account for it.
Has anyone found the audio on the TS850 somewhat tinny and noisy?
Question about receive quality on a TS850
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absorbentgnome
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Re: Question about receive quality on a TS850.
The spec
Sensitivity
0.25uV for S/N 10dB
Selectivity
SSB
2.5KHz for -6dB
4.2KHz for – 60dB
Image Ratio and IF Rejection
Better than 50dB
One fault I have had with low RX performance is mixer Q9, I could not fine any of the voltages to be wrong, but on replacing Q9 and all was will again.
It maybe worth checking VFO input on Gate G1 of Q9, as I remember you saying you had low TX power, if the VFO is low this will be the cause of both faults.
Sensitivity
0.25uV for S/N 10dB
Selectivity
SSB
2.5KHz for -6dB
4.2KHz for – 60dB
Image Ratio and IF Rejection
Better than 50dB
One fault I have had with low RX performance is mixer Q9, I could not fine any of the voltages to be wrong, but on replacing Q9 and all was will again.
It maybe worth checking VFO input on Gate G1 of Q9, as I remember you saying you had low TX power, if the VFO is low this will be the cause of both faults.
Rick.
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absorbentgnome
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Re: Question about receive quality on a TS850.
Ok thanks for the information Rick. I'm going out into the wilderness this weekend so I'm going to take the TS850 and a few other rigs and compare the sensitivity and quality in a low noise environment. It may not have a problem.
The low TX power problem is on the old TS520. Still haven't got round to preparing a post on it. Soon hopefully!Rick wrote: It maybe worth checking VFO input on Gate G1 of Q9, as I remember you saying you had low TX power, if the VFO is low this will be the cause of both faults.
Re: Question about receive quality on a TS850.
Sorry my error. I need to go to Specsavers lol. This is happens when you get as old as I am.
I read it as TS520 opps.
I do not know of any problems with the TS850, but will have a look in my Kenwood fault finding guide.
I read it as TS520 opps.
I do not know of any problems with the TS850, but will have a look in my Kenwood fault finding guide.
Rick.
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absorbentgnome
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Checked the receiver under low noise conditions and its fine.
A further problem has surfaced though - in FM receive mode, the AGC seems unstable. The signal fades and returns in an oscillating manner which is slow, then speeds up then slows down again. This affects signals around the S9 level and below. Strong signals do not have the problem. Any ideas what this could be?
There is a cap near the FM chip which looks suspiciously like the same make and type of one that I had to replace in the audio circuit due to leaking on the same board. Probably a good idea to replace anyway.
A further problem has surfaced though - in FM receive mode, the AGC seems unstable. The signal fades and returns in an oscillating manner which is slow, then speeds up then slows down again. This affects signals around the S9 level and below. Strong signals do not have the problem. Any ideas what this could be?
There is a cap near the FM chip which looks suspiciously like the same make and type of one that I had to replace in the audio circuit due to leaking on the same board. Probably a good idea to replace anyway.
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absorbentgnome
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Replaced cap C124 (underside was swollen and had reduced from 22uF to 15uF) on IF board and hoped for the best. Took a while for the problem to show itself but it was still there.
So I connected up my other kenwood with an antenna switch so I could definately check the problem was still there. Surprise surprise the fading effect (on known base stations) was there on both rigs! I'm sure it wasn't before ... wasn't I?
I think I've gone on a wild goose chase. 
So I connected up my other kenwood with an antenna switch so I could definately check the problem was still there. Surprise surprise the fading effect (on known base stations) was there on both rigs! I'm sure it wasn't before ... wasn't I?
I think I've gone on a wild goose chase.
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absorbentgnome
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The problem does seem better now. The cap C124 is across the 6V supply in the MC3357P circuit. Has anyone seen any effects of this cap drying out on a MC3357?
Since its across the supply rather than in the functional part of the circuit I would have thought that it could have lost a lot of capacitance and not had an effect.
Since its across the supply rather than in the functional part of the circuit I would have thought that it could have lost a lot of capacitance and not had an effect.
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absorbentgnome
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Re: 850
Indeed - I have replaced a number of caps on this rig. Luckily, someone else had already replaced the caps on the CAR board before much damage to the pcb was done. (its the one with the early DDS chips - got my fingers crossed for these ones!)
I think the problem is fixed now
