FT-707

Fehlfunktion am YAESU FT-707

Category:

Science & Technology

Tags:

• Fehlfunktion
• am
• YAESU
• FT-707

[dc0go]

Hello OM JI3LLL, thank you Sir for your wonderfull Tip's, i hope soon to replace the parts and an hope to send you a happy msg. Maybe if it's work we can test ist by a sked? vy 73 de DC0GO

[dc0go]

Hello OM, JI3LLL , yes Sir, I think there was the choice of components to the model not happy. One can recognize very well that it is related to the NF together, the RF meter shows the S-meter, so until the RX / TX switching everything still OK! My first thought was the relay's, but the cleaning did not improve. Now I've found a dry elektrolydkondensator and think it is basically a capacitor problem, but Ozi and multimeter tell me it would be all right. vy 73

[dc0go]

Hello OM, i dont think so, but i dont finde a shorty, the ar a very long switchover time between RX/TX, i think more that a "C"ondensor is defekt. I measured a lot, but found nothing. The error is not always the unfortunately makes it a patience game.

I'm thankful for every tip, vy 73 de DC0GO

[PY3NK]

Tenho um inteiro desses para venda no Brasil....

ótimo transeptor....73 von py3nk qrz.com

[eldorado303]

just the other day i worked a station using one of these. i looked it up and liked it. great audio on tx. i liked it. cheerio, ct2izo

[oz1dwf]

Remove the bottom cover. In the middle of the big circuit board you will find the relay. There is fault with the speaker does not end when you switch from TX to RX. I have experienced the same problem with my FT-707 gear. Remove the cover on the relay and the poles. Remember to put the small plastic cap back on after cleaning.

PS: If you did not added the FIX XTAL for each band, the frq read out swing when you activate FIX. It is standard and no errors on the radio.

Vy 73 de OZ1DWF, Leif.

[OsakaSakaiTube]

Hello OM, Hopefully the problem will go. I'm almost certain that the root cause can be logically spotted and rational fix to it can be applied. Regarding the scheduled QSO, unfortunately I do not have my station now.. but I'll be checking your update here.

The 707 was my very first rig and I did really enjoy ham radio with it (and had a same problem too) so I hope your 707 will show a full recovery. de JI3LLL

[OsakaSakaiTube]

... shows a tricky operation. If your problem still persists after replacing the defective cap, it's worthwhile checking the voltage of J7-Pin6 on AF board (RLCONT signal) on RX state. Ideally it should be 0V, but if it reads more than 2..3V, you can be almost sure that the culprit is the circuit formed by Q19, Q18, Q14. My wild guess at this stage is that Q18 is weakly pulling Q19.Base which is either caused by defective (low-hfe'ed) Q14, or R60 (15k) which is floating from Q18.Base.

de JI3LLL

[OsakaSakaiTube]

... still driving T/RX relays weak. And among many T/RX relays being driven by the Q19, RL01 on AF board happens to be the one whose off voltage is marginal to the residual weak driving voltage and is still holding contact even when you turning of the MOX switch. I checked the driving circuit and found first of all, there are error in the corresponding circuit in the user's manual (which is corrected in service manual), and the circuit comprised by Q14 and Q18 that are also driving the Q19 ...

[OsakaSakaiTube]

Hello OM, hopefully replacing the defective condensor will fix the problem. Yes, I can see your 707 is actually back in RX mode on at least RF to IF sections even while this problem is happening - as you said, S-meter is acting, and RIT is reacting. As your last part of the vid shows, its audio reluctantly comes back after a long while, which may suggest that relay driving transistor - these symptoms suggests that the RL driving transistor (Q19 on AF board) is not completely turning off ...