Replacing a VU meter (not fixing) Superscope CD330 by Marantz

[ms660]

Originally Posted by sourbiscuits

I am keen to ask - what are these two circuit errors related to? Also do you suggest that I modify anything?

They're related to the circuits in the schematic mentioned in Post#16, (RH channel line output and RH channel source monitoring etc which also includes the feed to the RH VU meter when switched to source monitoring) There might be other errors in the schematic (I haven't checked the schematic in full)

The errors mentioned aren't physical production errors, I checked the board layout etc in the service manual and those circuits checked out ok as previously mentioned.

You might only need to modify anything if fitting different types of VU meters.

Lawrence.

[sourbiscuits]

Thank you guys! I also followed the same logic that it's likely just a schematic error. I am still unsure if I should solder the pins back to the pads in post #12 (see photo labeled "pads")? I feel like there used to be more soldering tin there.

[peter_sol]

I suspect those are duplicate points or earth points. I wouldn't worry about them.

[sourbiscuits]

Hey guys. So my replacement VU came in last night. I soldered it, however, there seems to be something wrong with the signal coming out of the wire. Basically, I have a total three wires that are coming out of the PCB and were attached to the VU meter. There was also another wire (blue) that was only soldered to the VU meter and not to the PCB. There are two short wires (red and white). When I solder them to either side of the VU (L or R) the meter responds properly. However, the other (longer) white wire does not seem to do anything, regardless how I connect it to the rest of this curcuit. I did a multimeter test set on 20 v (DC) and the short wires give a reading of ~ 1 V. I can't seem to get anything out of the other wire. I am assuming that one is the positive treminal of the L channel, and the blue wire was the soldered to the common ground. I unfortunately did not seem to take a photo of how things were wired with the old VU ( even though I recall that I specifically did). Anyway, I can confirm the new VU is in good order and both needles are responding to signal. Should I tweak the trim pots of the VU adjustments or else what would you suggest to look at in order to fix this?

[ben]

maybe for a backlight bulb? In any case if it works, just enjoy it!

[DMcMahon]

Your YouTube video (Post 7) of the VU meter operation does not show a blue wire, unless it was attached across the back of the meters.

The CD330 circuit board diagram (wiring layout) shows 3 VU meter wires (red, white and red/white) connecting to the PCB plus a red/white link across the 2 meters (maybe the red/white link is the blue wire in your case).

No obvious VU meter backlight shown on schematic or wiring layout.

Did you not take a photo of the back of the VU meters showing the wiring connections before you disconnected the wires ?

David

[sourbiscuits]

Thank you David! I looked very thoroughly and eventually I found the photo I remembered taking. I am attaching it for reference. The positive terminal goes on the top right end and the blue one indicates where the ground is. The problem with the left channel signal was actually caused by me. As mentioned, I installed a switch which links line L out to R in to enable ping pong delay setup. I had to make room for the switch so I removed the battery check button. The signal of the left channel was actually going through there and I had it disconnected from the PCB. I currently have the vu installed and all works well. I am glad I can finally have this unit done as it's likely one of the tape decks I spent most time working on.