I just swapped the Transistors on PM01 since I figured it could be the problem, no luck...
Marantz 4300 no rear channels
- Thread starter goldswimmerb
- Start date
petehall347
the brandy coffee man
should be 2 boards looking at that one and also checking the manual .
there arent enough components on that board for 4 channels .
there arent enough components on that board for 4 channels .
Yeah there's two boards, ones LF LR and ones RF RR
I believe that takes out the BTL Phase Inverter board. At least there was a cap blown off of that board on my 4270 when I got it.
petehall347
the brandy coffee man
looking at the schematic confused me as it must be marked wrongly .
Yeah it is, the schematic has a typo
Replaced the capacitors and Transistors on the phase inverter board and still nothing.
The rear channel does output when in two channel mode, then in 4 channel mode there's not even DC offset at the rear after the relay closes.
The rear channel does output when in two channel mode, then in 4 channel mode there's not even DC offset at the rear after the relay closes.
ALRIGHT!
So some buffoon reversed the 2/4 switch in this unit, so I, like a fool, was trying to figure out my rear channels in 2 channel mode.
Now onto the actual problem... Rear left is very quiet, it's definitely in the preamp stage as it moves with the pre outs to the various main ins.
When I switch into 2ch mode on the front panel that channel gets very very crunchy. In discrete mode it's just quiet.
Maybe a bad diode or transistor in the preamp?
So some buffoon reversed the 2/4 switch in this unit, so I, like a fool, was trying to figure out my rear channels in 2 channel mode.
Now onto the actual problem... Rear left is very quiet, it's definitely in the preamp stage as it moves with the pre outs to the various main ins.
When I switch into 2ch mode on the front panel that channel gets very very crunchy. In discrete mode it's just quiet.
Maybe a bad diode or transistor in the preamp?
From the many 4270 and a 4300 I’ve been through, my experience is that the tone board is full of trouble maker transistors. I think every one I worked on had a problem in that damn board. I recommend taking it apart, it’s a bitch, recapping it, including the tantelums and replace every transistor while it’s apart because it’s a bitch to take apart. Did I mention, it’s a bitch.
The preamp board usually just likes new caps.
After that, any more weird issues are probably hiding in the DOLBY board.
Then a good power supply recap and may as well do the amps and you’re pretty good.
Once the tuner boards are recapped, she’ll be nice. The MPX board is a bitch. It’s under the AM board. Having the amp and power supply and AM board out or loose is the best way to get to it.
Get the inverter board and Phono board and you should be home free. Unless there are some tired transistors hiding out.
Piece of cake!
Enjoy.
It doesn't look thaaaaaaat bad.... The PU01 board in the 2325 was bad, this looks relatively standard aside from the angled board on the back end.
The angled board isn't that bad. Just take off the covers, pull the knobs, pull the faceplate, undo the nuts/washers on the tone control board, and the board comes out. Desolder the little vertical board, replace the stuff on it, call it a day. You'll need some bipolar caps but it's not wildly difficult. I did one the other day.
I have films that should fit there.
Hopefully its just a bad component on one of those boards looks like there's a ton of trouble makers.
So someone definitely worked on this unit before. Found a 2SC458 in my dead channel in the preamp, not sure why they would have replaced a 2SC1345 with a 2SC458. Tested fine in my cheap Transistor tester but I don't trust 458s in any application, especially ones where the original was rated for higher voltages.
Alright Update time!
No luck yet, rear left channel still is very very distorted and quiet. I Recapped and put new transistors in PD01. Next I'm going to go for the buffer PE01 board, which has way too many tantalums, VD1212s and 2SC1318/2sc1345s/2SA720s for comfort. Guessing my issue is here since there's not many other spots for it to be.
I also noticed the bad channel works just fine when immediately turned on, then after something heats up after a few seconds it gets crunchy.
No luck yet, rear left channel still is very very distorted and quiet. I Recapped and put new transistors in PD01. Next I'm going to go for the buffer PE01 board, which has way too many tantalums, VD1212s and 2SC1318/2sc1345s/2SA720s for comfort. Guessing my issue is here since there's not many other spots for it to be.
I also noticed the bad channel works just fine when immediately turned on, then after something heats up after a few seconds it gets crunchy.
Attachments
Well, i rebuilt the buffer/preamp board, and... Nothing, my problem actually moved channels on me. Now my dead channel is front left. Testing at the output of the PD0@ board gives me a hum in the dead channel so it has to be upstream from there... Any ideas?
Anyone know the preamp channel layout? I'm assuming ch1 is FR CH2 is FL CH3 is RR and CH4 is RL?