silent

Dear experts, I have a Sony MZ-RH1, now sadly no longer a guarantee, and I have two major problems with this device. 1st I built about a year ago an external battery pack for the Minidiscplayer, this consists of four 1.5 V batteries in series (not the really small ones, but the slightly larger; like in a portable CD-Player) with miniUSB connector. I can not say with 100% certainty, but I am of the opinion that the device can't be loaded from that time using the USB adapter from the socket. About PC mode, the loading works for some time, and on the external battery compartment also without problems. My question is, could it be that the charging circuitry is broken or wouldn't the player then load no more from the external package? The device loads as normal in the charging mode with indicator, display how long it will take, using the USB adapter with normal electricity does nothing. The MD player has an input with a voltage of 5V. My battery has a bit more. Maybe you can help me before I buy a new power supply, which may then be in vain. 2nd For some time the Minidiscplayer jumps, with some songs I've played with Sonic Stage on a Hi-MD. MP3,Atrac - does not matter. Some songs he plays, then stops and jumps to a different location on the MD. I have already cleaned the lens, it could be that the laser unit is faulty, how can I test it? Many songs go smoothly, including forward and rewind, and some did not even start or stop in the middle. If you know these problems and my suspicions are correct, I would like to know how it is with the change of the charging circuitry or the laser unit. How much does something like this cost and can I change it myself? Sony offers a so-called flat rate repair for 180 Euros, but that is too expensive. I have bought a new battery because I thought maybe thats the problem, but unfortunately this has been of no use. I would be very happy to use the RH1, I love this player, it is responsible for recording interviews etc and the sound quality is really bombastic. I hope there is an affordable solution for my problems. Thank you already for your help greetings Manfred P.S. Sorry for my really bad english, i got help from the google translator and I know, that is not all in the correct english grammar, sorry for that.