Rock-ola 480 amplifier has no audio after recap and service

[Ron Rich]

Well,
I can help a little-- Your speakers can not be accurately "measured" with any volt/ohm meter! You need a "Wheatstone meter" for that. Sounds as if they are in "proper range" to me-- And-- just me-- but as far as I'm concerned, NO "sandpaper", or "steel wool", of any kind, belongs around anything electronic, ever ! I use only Crocus Cloth, when necessary. Ron Rich

[jollyjon]

Hey Ron, I missed your post as I was typing my last. What is AVC and what area would it be located in an amplifier? My other jukebox amplifier does not increase in volume in last 2 seconds when it's switched off. Maybe it has the same problem but does have the symptom of the other but just has a low volume in common. I did mention in my first post I had a cd player connected but you probably missed it as I babel on a bit sometimes.

Appreciate your help and advise if you can direct me where to search or material to read to gain an understanding of what AVC is.

[Ron Rich]

I do recall you mentioning that earlier--just forgot it--
AVC-- Automatic Volume Control -- Aka- "Loudness control" & AGC = Auto. Gain Control -- Hiding some where within the amp--as I said-I don't work on them--- Ron Rich

[jukenorman]

I do work on these amps from time to time but in this instance it's quite difficult to help you because what you are attempting is "abnormal". Now if you were trying to interface a CD player to a working vinyl jukebox, that would be quite different because the jukebox would still operate as Rock-Ola designed it and we can relate to that. I'm not saying that what you are attempting is not possible, but I'm sorry to say that I think it's difficult to provide meaningful guidance here without getting bogged down in the theory of amplifier operation and design - with somebody who by his own admission is a novice. Please don't take this the wrong way, but I suspect that you have been too ambitious!

Norman.

[jollyjon]

BREAK THRU: Ron's suggestion it may be related to AVC got me thinking about the pre-amplifier where the AVC switch is located on. To my awareness the CD signal does not require a pre-amp and the CD signal was tapped into the same line before the tone control board but after the pre-amp. My jukebox went into the garage and stayed there for 15 years unused in 2005 when I nearly killed myself in a car accident and became an epileptic with some memory loss of that year. When I started to get my jukebox working I tried to get it as close to the schematic as I could. I did a recap and also noticed a few wires cut. I could not remember what I did to it 17 years ago or if I even cut those wires or even if it was faulty at all back then before I put it in garage to store. I just reconnected them thinking it was the best thing to do as part of getting it working. Today I found out those wires were cut for a purpose by the jukebox company that I bought it from that did the CD conversion.

After I found the fault of the initial very loud machine gun like buzz thru one of the channel, which was a faulty power transistor, I had no music despite all the voltage levels being as they should. The error (of my own) was that one of the wires was for the mute board and it's used to mute any sound when a record is not playing. As I bought it with CD stacker and vinyl mech removed, the wire was cut as it's not needed. When I cut it off after I had no music the music came back. That mistake cost me about 30 hours to figure out the cause and should have never reconnected it. The second mistake I made, much like that one, is that the ground wire was cut to the pre-amp and I reconnected it the beginning along with the mute wire. As Ron suggested it may be the AVC, I started checking the ac voltage of CD signal that started at 150mV on player but when tested plugged in amp it measured much less. I thought that maybe the powered pre-amp board was maybe having an effect being tapped into the same wire as CD. My music was low volume and muffled out treble. I didn't bother to cut the ground wire to the pre-amp board, or the 15V power or signal output, I just pulled the whole plug from that board as it wasn't needed. From what I saw in the schematic, the signal voltage for the record input was much lower at about 10mV - hence the need for a pre-amp. I turned the jukebox back on and WA-LAH, it's really loud and clear. In hindsight I'm ashamed I wasted 90 hours on it when I could have done it in 3 hours if I didn't reconnect the wires as per the schematic and never lost any memory from my car accident. Now that I know exactly what it was I could have fixed and recapped in 30mins.

Though Ron and Norman didn't help directly solve my problems, I still much appreciate your indirect help as any insight will increase my knowledge and every bit helps in gaining understanding. No time to chat any longer - it's time for me to crank up the volume any annoy my housemates with something greater then my mini-hifi.

[Ron Rich]

Glad it's working-- but once again- I think had you done as requested when you first posted, we all would have "wasted" much less time-- if you had read the Hi Newbies post,as requested -- and told us the jukebox was nothing more then a cabinet/audio system. Enjoy your music ! Ron Rich