Kenwood Twins R-599D/T-599D problems with S-Meter...FIXED!

[N2JPR]

I'm new to this board and wondering if anyone has experience with troubleshooting the R-599D receiver. I cannot get the S-Meter to respond to received signals. The rig has plenty of sensitivity and I can hear weak CW signals with the RF Gain control at mid-position. I have troubleshot the IF board. Q4 and Q5 checkout fine for DC bias. I have replaced them both. D11 and D12 also replaced. The RF Gain control works fine (makes the needle go full scale on CCW and 0 on full CW rotation), but no CW signal movement.
I also have an IF AC signal to the base of Q4 of about 100 mV p-p that follows the received audio, yet the collector of Q4 does not amplify this signal. The adjustment of VR3 has no effect on S-Meter movement. If I inject a high level RF signal to the antenna (around 0 dbM) I can get the S-Meter to move slightly.

Where should I go from here? I'm stumped. Lou N2JPR

11-13-04

Well, after 2 weeks of occasional evenings and 2 orders from Mouser, the rig is fixed and working well. The final fix was a soft Q3 (NTE85) transistor and open AGC detector diodes D1 and D2 (NTE110). I had also replaced Q4 and Q5 during my troubleshooting with no change in circuit function. After adjusting VR1 and VR3 on the IF board and VR1 on the RF amp board, I have significantly increased the sensitivity and the S-meter deflection. This rig is amazing and flat out the most selective and sensitive rig I've ever used. The number of front panel controls is borderline overkill, including a squelch control. Oh well, I've got alot of spare parts left for future IF board troubleshooting.
73, Lou N2JPR