On 2 January 2017 at 18:21, Robert Atkinson <robert8rpi@yahoo.co.uk> wrote: > I've a spare knob and it's on it's way to Dave. f > Cheers Robert. I'll send you some money. Drop me a private email with your PayPal address. > 5370 counters do seem to run hot so I don't think you have a fault. As > suggested a little external airflow can help a lot. > > Robert G8RPI. > I'll have to check now I have put a variac on the supply voltage to the equipment. I set the variac last night, and have set my Tektrononix handheld to record min/max/average readings So far * Min = 216.71 * Max = 232.75 * Average = 227.88 * Min-Max=16.04. Obviously the change of 16.04 V is a bit lower than the real swing, as the variac is reducing this. Perhaps I might need to increase the variac voltage slightly, but I suspect that running a significantly lower voltage than before can only help. Maybe just a bit too low though. I also ordered a couple of those GPIB extenders. It would seem totally impossbile to get a GPIB cable on otherwise. Sticking the GPIB connect right next to the heatsink, with the cables coming out the side of the heatsink seems a bit odd. Unless there are any cables which come out the other side, so away from the heatsink. Anyway, I have an HP and a Keysight 10834A on order, which should give me enough room to get a GPIB cable out. A 5370B without a GPIB connection is a bit of a useless bit of kit. Dave