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Marantz 2250B case screw

gary7

gary7

AK Subscriber
Subscriber
Picked up a Marantz 2250B. Managed to strip the head of a case screw. Manual calls it a B4X6. Could not find them. Anyone know what a replacement size would be?
 
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Question I have is about the main in/pre out jacks. It plays without any jumpers. The manual says you can hook a tape deck to it & mod the recording. But no need for jumpers? Can it be used as a straight preamp?
 
gary7 said:
It plays without any jumpers.
Click to expand...
When there is no plug inserted the contact internally connects as shown in the schematic. When a plug is inserted, the internal jumper connection is broken and connected to the plug inserted. You can use just the Preamp by connecting a stereo RCA cable from the L/R Preout jacks to the inputs of your separate power amp.

upload_2022-10-26_21-8-4.png
 
dankik said:
When there is no plug inserted the contact internally connects as shown in the schematic. When a plug is inserted, the internal jumper connection is broken and connected to the plug inserted. You can use just the Preamp by connecting a stereo RCA cable from the L/R Preout jacks to the inputs of your separate power amp.

View attachment 2698571
Click to expand...
Is this a high res schematic from the AK database? I have only seen the switching contacts on the Main In side. This shows them as well on the preamp side. Or have I just been blind - quite possible!! Your advice is still quite correct though.

EDIT: I just looked at my two copies of the SM and on both the general schematic and the full one the preamp jacks are NOT switching.
 
rBuckner said:
EDIT: I just looked at my two copies of the SM and on both the general schematic and the full one the preamp jacks are NOT switching.
Click to expand...
@rBuckner, yes that was from the HiRes schematic from AK. Shown below is from the 2250B SM schematic on AK which shows that the Preamp is always connected to the Pre Out. What that means is when you plug in your RCA cable into the Pre Out jack to go to an external amp, the Main amp is still connected and will also get audio. You would need to put a shorting plug into the Main input to disengage the audio from going to the Main amp. Does that make sense? If you had the old external jumper style Pre Out/Main In plug, when you unplugged it the input to the Main would be open. If you have a 2250B or similar on your bench you could verify this.

upload_2022-10-27_7-36-23.png

Here's something else that is interesting. The schematic from my 2252B has yet another variation where inserting the plug into the Pre Out will break a connection on the jack, but it is not wired up to use that terminal. Curious :dunno:
upload_2022-10-27_7-56-56.png
 
Last edited:
^^^ Yes your explanation makes sense. I wonder if that 2252B schematic is wrong? Could be they just wanted to keep it simple and just use the same jacks. Kind of doubtful as they don't even a half inch of extra wire length anywhere to cut costs!
 
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