Rich_D Posted August 2, 2023 Share Posted August 2, 2023 (edited) I have a very old ProMedia 2.1 THX system, see pics. It has the original preamp input which has actually never given me problems, nor has the control module. Upon moving it from one room to another, when I power on the system I get a very loud thump or whomp sound from the sub. It's rhythmic like a steady heartbeat. Support said it's in the amp but it's too old and unserviceable. I have the circuit boards apart but I don't see any problems from visual inspection. Caps look ok. Can anyone direct me where I might start looking for the problem? Edited August 3, 2023 by Rich_D more info Quote Link to comment Share on other sites More sharing options...
OO1 Posted August 4, 2023 Share Posted August 4, 2023 these subs come up for sale on Ebay , at very low prices Quote Link to comment Share on other sites More sharing options...
Rich_D Posted August 4, 2023 Author Share Posted August 4, 2023 16 hours ago, OO1 said: these subs come up for sale on Ebay , at very low prices Ok thanks, I'll start an Ebay watch. I can't bring myself to throw away all this electronics though. Maybe I can see it for parts/repair. Quote Link to comment Share on other sites More sharing options...
OO1 Posted August 4, 2023 Share Posted August 4, 2023 1 minute ago, Rich_D said: Ok thanks, I'll start an Ebay watch. perfect Quote Link to comment Share on other sites More sharing options...
babadono Posted August 4, 2023 Share Posted August 4, 2023 for shits and giggles I'd replace the large electrolytic caps in power supply section to see if that magically fixes it. Those large indigo colored cans. Match the voltage and capacitance values. A little higher voltage value on the replacements is OK. I would try to get 105 C temperature devices if the originals are not and are 85 C devices. Be careful with sizing of replacements, make sure they will fit. Have you tried to find a service manual? Quote Link to comment Share on other sites More sharing options...
babadono Posted August 4, 2023 Share Posted August 4, 2023 There is a 3 pin cable/connector dis connected. You do know that and /or did it intentionally? Quote Link to comment Share on other sites More sharing options...
Rich_D Posted August 4, 2023 Author Share Posted August 4, 2023 1 hour ago, babadono said: for shits and giggles I'd replace the large electrolytic caps in power supply section to see if that magically fixes it. Those large indigo colored cans. Match the voltage and capacitance values. A little higher voltage value on the replacements is OK. I would try to get 105 C temperature devices if the originals are not and are 85 C devices. Be careful with sizing of replacements, make sure they will fit. Have you tried to find a service manual? Yeah I have a schematic for it. Thanks for all the tips. I wasn't thinking power supply because I have all lights and power but I really don't know much about these circuits. Quote Link to comment Share on other sites More sharing options...
Rich_D Posted August 4, 2023 Author Share Posted August 4, 2023 1 hour ago, babadono said: There is a 3 pin cable/connector dis connected. You do know that and /or did it intentionally? Yeah, that was me starting to disassemble before I remembered to take pics for reassembly and to post here. Quote Link to comment Share on other sites More sharing options...
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