Marantz 1180DC restoration
- Thread starter cbusuttil
- Start date
Thank you for this thread! It has been very helpful to me in restoring an 1180DC.
I have a hopefully easy question. There is an orange wire on the preamp board terminated between SJ02 and SJ03, and when my unit arrived it had many terrible repair attempts with broken wires, wires soldered in the wrong locations, etc. This one in particular was soldered to the tape 2 monitor out, right channel, and the right channels tape monitor 2 in and out were jumpered together. I am assuming none of this was correct, but I can't find this orange wire anywhere in the service manual.
Can anyone help me identify where the small white cable protruding from the end of this orange cable should actually terminate? Thanks in advance.
I have a hopefully easy question. There is an orange wire on the preamp board terminated between SJ02 and SJ03, and when my unit arrived it had many terrible repair attempts with broken wires, wires soldered in the wrong locations, etc. This one in particular was soldered to the tape 2 monitor out, right channel, and the right channels tape monitor 2 in and out were jumpered together. I am assuming none of this was correct, but I can't find this orange wire anywhere in the service manual.
Can anyone help me identify where the small white cable protruding from the end of this orange cable should actually terminate? Thanks in advance.
what trimpot is that? may i have the brand and spec like ohm?
cbusuttil
Active Member
i think it's made by Bourns, i don't remember the value though. I used the same values as the originals. here's a link to something similar...
Hello, if i cannot find 16v, can i use same 10uF but 25v?
cbusuttil
Active Member
I have to be honest with you.....you got me genuinely worried with that question. If you do not know the answer to that question, I highly suggest that you refrain from tinkering with this or any amplifier before you get to know basic electronics as you might hurt yourself; there are high voltages inside and at times their terminals are directly exposed. Now, to answer your query, yes you can use ones with 25v but i suggest you confirm the actual voltage that is present, then double the capacitor voltage. Example, if the voltage present is, say 16v, you put a cap with 25v. Another example...if you have a 5v present across a capacitor, the general rule of thumb would be to put a 10v one. The reason has to do with maintaining the oxide layer in a healthy condition. The capacitors in question are non polarised as they couple AC. You have to see the schematic to get an idea of the actual voltage that would be passing through but if i remember correctly, those are across the input of the main amp, thus these would see very low AC voltage. I would strictly stick to the double working voltage theory or at least match the originals.
Thank you, i know a little bit basic of electronic, i know how to solder, desolder, and know how to use multimeter. I just dont know the basic of amplifier. Still learning...
I plan to make a new thread for recap and restore my 1180dc, and still collecting data.
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The 1180 is not a amp for someone to learn on if take it to a tech if you are comfortable with electronics and schematics then different then ok I generally keep to the same voltage or one higher but it’s important to know what type of cap to buy for the location in the amp also so there’s more to it - a tech knows these things if you want to tinker maybe try a smaller less expensive one for now that is easy to work on
cbusuttil
Active Member
Understood. There are plenty of basic tutorials on components and how they function. Be sure to master that before attempting to restore your 1180.
cbusuttil
Active Member
cbusuttil
Active Member
Fully agreed. The 1180 is not an amp for the faint hearted. It can mind boggle even very experienced techs. I suggest that you buy something very simple and practice on that. It's not just soldering and desoldering components... some components are obsolete and you would need to find substitutes and understand WHY those substitutes work.. kind of, understand thoroughly all datasheets etc not just put substitutes because some other individual told you so. Mind you, I am happy for you that you are interested in these things and willing to learn. Its just that the candidate in subject (1180DC) is a very inappropriate amp to learn on not only because it is decently complex, but because it's valuable.
cbusuttil
Active Member
You are welcome! Sorry for my late reply but it seems I did not see your message. I'll keep you in my thoughts whenever i need to get inside my 1180DC again and will check for you. So far, 3 years of everyday use with no problems whatsoever.
AndrewD4492
New Member
Hi all
Im in the middle of refurbing one of these (1180DC). So far sounds great, but now at mid volume and above I'm getting distortion on both channels that is worse on the left. I can reduce volume and distortion goes. Cant get volume past 10.00 o'clock. I was thinking that the MV1 varistors are not doing their job. However at a loss with what I can replace them with. Any ideas? If its not them - I am at a loss of where to go. Please refer me to another thread if more appropriate.
I dont have an oscilloscope so can see whats happening live. I have replaced all transistors with new including small signal, medium drivers and power trannies. Also all caps. Help in troubleshooting need! Thanks
Im in the middle of refurbing one of these (1180DC). So far sounds great, but now at mid volume and above I'm getting distortion on both channels that is worse on the left. I can reduce volume and distortion goes. Cant get volume past 10.00 o'clock. I was thinking that the MV1 varistors are not doing their job. However at a loss with what I can replace them with. Any ideas? If its not them - I am at a loss of where to go. Please refer me to another thread if more appropriate.
I dont have an oscilloscope so can see whats happening live. I have replaced all transistors with new including small signal, medium drivers and power trannies. Also all caps. Help in troubleshooting need! Thanks
Have you established if the problem is in the power or pre amp? Or is the issue with both? This will help track down your problem
AndrewD4492
New Member
definately power amp. I have tested output of preamp with external power amp - and its completely fine. I have isolated relay and peak indicator board and the static distortion is still there same as before. So conclusion through isolation is its in the power amp board somewhere. Sense is that there is either too much gain in mid driver stage. or the mid driver transistors are overloading. However I have replaced mid drivers with alternatives and problem remains. so ??
AndrewD4492
New Member
perhaps it the MV1 varistors, as I am having trouble also getting a stable offset voltage even after an hour of running?? If so can I sub these with IN4004's as the MV1's are no longer available and obsolete?
AndrewD4492
New Member
Perhaps it the MV1 varistors that are playing up, but if they are the problem then what to replace them with as they are long gone in availability. Cant seem to get a stable offset voltage either.... it varies all the time - nothing critical but wavers +/- 10mV
Can you share what transistor substitutes you used first
Is the distortion on both channel?
Please double check again transistor pin orientation and if any tracks are damaged where those diodes sit on the trace side often there is glue there and they can be damaged
If you replace mv1 with 1n4148 you’ll need to replace a few resistors as will likely increase the bias if they are in the bias circuit I don’t recall which ones are impacted I don’t think the distortion is caused by mv1
Please double check again transistor pin orientation and if any tracks are damaged where those diodes sit on the trace side often there is glue there and they can be damaged
If you replace mv1 with 1n4148 you’ll need to replace a few resistors as will likely increase the bias if they are in the bias circuit I don’t recall which ones are impacted I don’t think the distortion is caused by mv1
How are the zener diodes on p700?
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