Brian Malman
Member
Hi,
My 2238 restoration is finally complete. I've done a complete recap and replaced most of the diodes on the P800 power supply board. I'm using the original 10,000uF / 50V value for the new power supply caps. I also stayed with the original values of the caps on the P800 board, only increasing their voltages.
Basically, the lamps flicker and dim out slightly and dance along with the music - most noticeably when the amp is pushed hard and short bursts of power are called for. In other words, it seems like a lack of capacitance in the power supply or a sag in the rectification or something like that, even though these are just lamps we're talking about. It's like all the power is being used by the amp and the lamps are losing out because of it.
They are all brand new 8V/200mA incandescent fuse lamps (5 behind the dial and 1 behind each meter). I'm pretty sure the unit did this prior to the restoration though, so I'm not entirely sure whether or not this is just normal for the 2238. It's rather subtle but it's annoying enough to be noticeable. I checked all the wires to make sure they weren't broken or cracked at the posts and all of the connections were fine. Could this situation have something to do with a specific capacitor on the P800 board that feeds the lamp circuit that might benefit from an increase in capacitance?
I've seen posts here saying the flickering could have to do with a bad power switch, but the effect only happens to my unit at high volume levels. The only other thought I had, has to do with what I've seen in some of the 22xx series Marantz restorations online. Essentially, some of these receivers have very small electrolytic capacitors connected across the leads of the meters. I don't quite understand how this could possibly affect the lamps, but it's certainly something that I've been curious about, as the effect is most noticeable on the meter backlighting.
Would replacing the incandescents with warm white LED replacements be a possible solution, since they draw far less current / use less power?
What about a power supply bypass? Maybe smaller film caps in parallel with the main p.s. electrolytics could help to speed things up (i.e. more instantaneous charging)?
Thanks!
Brian
My 2238 restoration is finally complete. I've done a complete recap and replaced most of the diodes on the P800 power supply board. I'm using the original 10,000uF / 50V value for the new power supply caps. I also stayed with the original values of the caps on the P800 board, only increasing their voltages.
Basically, the lamps flicker and dim out slightly and dance along with the music - most noticeably when the amp is pushed hard and short bursts of power are called for. In other words, it seems like a lack of capacitance in the power supply or a sag in the rectification or something like that, even though these are just lamps we're talking about. It's like all the power is being used by the amp and the lamps are losing out because of it.
They are all brand new 8V/200mA incandescent fuse lamps (5 behind the dial and 1 behind each meter). I'm pretty sure the unit did this prior to the restoration though, so I'm not entirely sure whether or not this is just normal for the 2238. It's rather subtle but it's annoying enough to be noticeable. I checked all the wires to make sure they weren't broken or cracked at the posts and all of the connections were fine. Could this situation have something to do with a specific capacitor on the P800 board that feeds the lamp circuit that might benefit from an increase in capacitance?
I've seen posts here saying the flickering could have to do with a bad power switch, but the effect only happens to my unit at high volume levels. The only other thought I had, has to do with what I've seen in some of the 22xx series Marantz restorations online. Essentially, some of these receivers have very small electrolytic capacitors connected across the leads of the meters. I don't quite understand how this could possibly affect the lamps, but it's certainly something that I've been curious about, as the effect is most noticeable on the meter backlighting.
Would replacing the incandescents with warm white LED replacements be a possible solution, since they draw far less current / use less power?
What about a power supply bypass? Maybe smaller film caps in parallel with the main p.s. electrolytics could help to speed things up (i.e. more instantaneous charging)?
Thanks!
Brian
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