Re: Intermitten tx
The original PTT switch used in the HM-151 mic'swas not sealed and had a cheap actuator design. Icom started shipping a better sealed switch for repair parts in 2007 I think. It was an ALPS SKQJLBA010, available from Mouser.com, although it is currently backordered, but they have SKQJLAA010 in stock, which is identical except with a black instead of gray actuator stem.
The switch is easy to replace, however it is important to observe the manufacturer's soldering instructions, available in the datasheet on Mouser's web site at the link above. It specifies a maximum soldering iron tip temperature of 350 degrees C, using no more than a 20 watt iron applied for a maximum of 3 seconds to each lead. Exceeding these limits can cause the aluminum snap disk inside the switch to oxidize and cause premature failure or intermittent operation.
Since the old switch is not sealed it can often be "repaired" temporarily by squirting a good quality contact cleaner such as Deoxit 5 into the switch and repeatedly pushing the plunger to help clean the oxidation. However, the switch should be replaced soon after it is cleaned. The new switches are sealed and cannot be cleaned.