Mark V

Problems

Malfunction of 1000MP Mk V Antenna Tuner

Problem: Two weeks ago I had a malfunction of the Mark V antenna tuner. While tuning with low power of 25 Watts the tuner made a curious noise and it went to smell (stink). After that I could not tune properly, even not a dummy load. The curious noise kept on. The failure was a coil in the antenna tuner of the Mark V, which was built to
close to the PCB.

Solution: During tuning there happened to be a flash-over (a short circuit between the coil and the PCB) which apparently caused the smell and the malfunction. On the upper side of the antenna tuner we could not see anything which could have been the reason. However on the underside of the antenna tuner we could see a kind of short circuit (a black spot) of the PCB. We mounted the coil more upwards from the PCB. In this way there is no short circuit possible between the coil and the PCB. We cleaned the PCB and checked the other coils. The antenna tuner is working again! Perhaps this information is of your interest.

How to Avoid the Problem: With Menu 4-0 you could set the OUTPUT level on 10, 75 or 200 Watts.

Independent from 4-0 you are able to set the TUNE level on 10, 75 or 200 Watts with menu 4-3.With VR3003, VR3006 and VR3007 on the RF Unit board you are able to adjust these settings independent from each other. I did this for the following purpose:

I use my Mark V as exciter for the Alpha 91b.I adjusted with VR3007 the 75 Watts down to 25 Watts. Menu 4-0 and 4-3 I set to 75 Watts. In combination with the linear amplifier I don't have to be afraid to give too much input (e.g. 200 Watts). When I set 4-0 and 4-3 to 10 Watts and use the linear I have an output of about 400 Watts. When I set 4-0 and 4-3 to 75 Watts (in my case this is 25 Watts) I have more output, but still on the safe side. I never have to be afraid to use too much input and overload the linear. Never more then 25 Watts input for the 91b. This makes a very clean signal. With Class-A too! And I don't need the ALC-circuit between the Mark V and the 91b.

Without the linear I could set 4-0 and 4-3 to 200 Watts again. This is one of the great features of the 1000MP!