UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Hameg HM307-3 Cleaning and Repair

WaveyDipole · 28th May 2019, 9:43 am

That doesn't leave much in terms of components. From the board layout the it looks like you might have have the DIL version of the uA741. If it is fitted into a socket then it may just need reseating. On the other hand, if it is soldered in, then unless your "other Hameg scope" is a parts donor, I'm not sure I would be willing to disturb a working scope. 741 op amps (uA741C/N, LM741C/N, CA741C/N) are still available to buy. The metal can version tends to be quite pricey but the plastic DIL version is quite cheap so this shouldn't be too much of a problem to replace if that's the problem.

With that kind of a voltage drop, T301 must be getting rather hot?

BTW, is anyone else surprised that C313 is rated to only 1kV? Isn't that pushing it to the wire a bit? Probably down to the price of capacitors in the day, but I would have thought a 2kV would make more sense here?

28th May 2019, 9:43 am	#39
WaveyDipole Nonode Join Date: Mar 2013 Location: Leicester, UK Posts: 2,535	Re: Hameg HM307-3 Cleaning and Repair That doesn't leave much in terms of components. From the board layout the it looks like you might have have the DIL version of the uA741. If it is fitted into a socket then it may just need reseating. On the other hand, if it is soldered in, then unless your "other Hameg scope" is a parts donor, I'm not sure I would be willing to disturb a working scope. 741 op amps (uA741C/N, LM741C/N, CA741C/N) are still available to buy. The metal can version tends to be quite pricey but the plastic DIL version is quite cheap so this shouldn't be too much of a problem to replace if that's the problem. With that kind of a voltage drop, T301 must be getting rather hot? BTW, is anyone else surprised that C313 is rated to only 1kV? Isn't that pushing it to the wire a bit? Probably down to the price of capacitors in the day, but I would have thought a 2kV would make more sense here? Last edited by WaveyDipole; 28th May 2019 at 9:48 am.