"Peter Hoon" <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- Problem #1: Our TR4-C has reduced receiver sensitivity on all bands after alignment, switch contact cleaning and retubing.
20M and 40M produce 180 and 160 CW watts out respectively. Good SSB audio on the air has been reported on 20M and 40M. We have strong reason to believe AM is working OK on 20M and 40M. Problem #2: We also have less than one or two watts output on 80 M and 10 M CW. We are limited to 70 to 75 CW watts out on 15M. Would appreciate diagnostic trouble shooting paths to pursue. The Details We have cleaned all switch contacts with initally Tarnall then tooth pick with De-OX-It. Each side of the electrolytic multi-section in Xmtr was tested for leakage, and one 10 uF 25 V was replaced; others tested good, no leakage. All other tubular 200 volt and small electrolytics on circuit boards in xmtr were tested for ESR, and were fine. All tubes were tested with a lab analyzer tube tester (calibrated) Triplett 3444 for leakage, gas and transconductance, and tubes that tested at the high GM end of the Triplett roll chart range were installed. (However, we have previously tested a 6C4 which tested good, but performed defective, so would appreciate specific tubes we might substitute. Our tester may have indicated false positives for one or more 7 or 9 pin minatures. We are certain that the finals are fine, since we have seen 180 watts on 20M CW into an antenna, and have received S-9 SSB signal reports and excellent audio.) Final tubes were matched within plus minus 4 mills at the same bias, and within 5% on transconductance, and all three are excellent performers. Final Grid bias was properly set as described in the manual, and neutralization was successfully performed as described in the TR4-C manual. Rig output under load was compared with a second tested AC4 Pwr Supply, so our AC4 used with this rig is holding load fine with no hum or evidence of problems. The rig passed all cold resistance tests as described in the manual. The rig passed successfully all alignment steps as described in the manual (we did a complete alignment, all steps). Xtals in the converter stage (hetrodyne Osc.) associated with V!, 6EA8, were withdrawn and examined for corrosion, and buffed with skotch brite. This did not resolve problems. However, the Xtals have not been individually tested. Plate meter is indicating correctly. S meter shows S-9 with built in calibrator signal, and was calibrated during alignment successfully according to the manual. S meter appears to be mechanically and electronically working OK. A calibrated Wavetek digital signal generator confirmed lack of receive sensitivity: On 40 M at 7.1 Mhz, we have 1.5 mV produces S3, 4.0 mV produces S5 and 10 mV produces S7. On 20M at 14.1 Mhz, we have 1.5 mV produces S4, 4.0 mV produces S5 and 10 mV produces S9. The TR4-C receiver is speced at .5 uV for 10 db S/N and we have nothing remotely close to this spec. Thank you in advance for your suggestions and ideas. We will report back to you here. Max, N0HU Peter, VE1CHS Nederland, Colorado ---------------------------------------------------------------------- Submissions: [email protected] Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net ----------------------------------------------------------------------
