Hi all!
Have 2 pcs of Marantz SR-7012 receivers with the very same problem. Both detect DC at the output and go into Protection. Seems to be a typical situation where power amp and particular power transistors are blown. But not this time.
Here we have random DC Protection. Sometimes it is able to play through ALL channels maybe for half an hour, sometimes for 10 seconds.
Going deeper - checked DCDET1 and DCDET2 protection signals from Power Amp PCBA. Here we have yellow and blue signals resp. DCDET1 and DCDET2 over the time period. Notice 2 sec/div time scale. Seems to be quasi-DC spikes.
https://prnt.sc/uuxzm5
Sometime they are OK:
https://prnt.sc/uuy0pq
Furthermore, we have these spikes more noisy also on the INPUT connector of the Power Amp (checked with this connector disconnected from PA) and even Pre-Out RCA connectors at the back of receiver (blue print, yellow - DCDET1 of +60V as the Inputs are disconnected):
https://prnt.sc/uuy1jj
Direct and Pure Direct modes do not influence, Resets and other stuff like plugging all the connectors, too. Tried reflowing DSP (4 pcs at all) with hot air but spikes still show. Now seems to be more on startup after ~30 sec.
Maybe someone had the same situation and could share the experience.
Have 2 pcs of Marantz SR-7012 receivers with the very same problem. Both detect DC at the output and go into Protection. Seems to be a typical situation where power amp and particular power transistors are blown. But not this time.
Here we have random DC Protection. Sometimes it is able to play through ALL channels maybe for half an hour, sometimes for 10 seconds.
Going deeper - checked DCDET1 and DCDET2 protection signals from Power Amp PCBA. Here we have yellow and blue signals resp. DCDET1 and DCDET2 over the time period. Notice 2 sec/div time scale. Seems to be quasi-DC spikes.
https://prnt.sc/uuxzm5
Sometime they are OK:
https://prnt.sc/uuy0pq
Furthermore, we have these spikes more noisy also on the INPUT connector of the Power Amp (checked with this connector disconnected from PA) and even Pre-Out RCA connectors at the back of receiver (blue print, yellow - DCDET1 of +60V as the Inputs are disconnected):
https://prnt.sc/uuy1jj
Direct and Pure Direct modes do not influence, Resets and other stuff like plugging all the connectors, too. Tried reflowing DSP (4 pcs at all) with hot air but spikes still show. Now seems to be more on startup after ~30 sec.
Maybe someone had the same situation and could share the experience.