Revox A720 reception problem only mono no stereo - UK Vintage Radio Repair and Restoration Discussion Forum

Salvatore79 · 29th Aug 2019, 5:41 pm

Hi all forum friends and well found, now I follow the forum for a long time and I want to say that you are fantastic, but let's get to the problem, as from the title today I have in my hands a Revox A720 Pre-tuner that at first sight aesthetically perfect, I state that the device was a gift to me from my passionate uncle in the audio field, I was very happy to have it reading many excellent reviews on the pre revoxes of the time, I did not expect perhaps perfect would be missed ... given the age, but I I immediately start a first test but the device does not switch on, so opening it to a visual check I see nothing, but a check on the 220v line fuses I notice that one was corroded, I clean the connections well and put the fuse back .. now the appliance switches on, all power supply voltages are normal, the nixie display and the search command work perfectly, so I connect the outputs to the amplifier and attach an antenna, perfect audio result on both channels, the only scarce problem ee only mono reception, equipped with services manual that I am attaching, the device is well divided on single cards, the cards that concern the reception are 2-3, A6 IF amplifier and demodulator card, A7 stereo decoder card, maybe even some other card is interested in receiving, I ask for help to you more experienced, I have heard a lot about bad tantalum but it has a control to the capacimetro would be good (welded to the circuit). I replaced C35 on A6 in strong loss with no result, replaced also C20 on A7 but still no stereo reception, but only mono, now I'm a bit perplexed visually and everything ok but I at least hope that some capacitor on the path of the channel is at a loss, I ask you friends of the forum for help and thank you in advance ...

Salvatore79 · 29th Aug 2019, 7:04 pm

The pdf file is too big, could I link?

Nuvistor · 29th Aug 2019, 7:54 pm

Will the PDF compress using a ZIP type application? May be small enough to upload.

Salvatore79 · 29th Aug 2019, 9:44 pm

Unfortunately, even converting the file to rar does not give me the possibility to upload it ... too big

29th Aug 2019, 5:41 pm	#1
Salvatore79 Retired Dormant Member Join Date: May 2019 Location: Termini Imerese, Palermo, Sicily Posts: 8	Revox A720 reception problem only mono no stereo Hi all forum friends and well found, now I follow the forum for a long time and I want to say that you are fantastic, but let's get to the problem, as from the title today I have in my hands a Revox A720 Pre-tuner that at first sight aesthetically perfect, I state that the device was a gift to me from my passionate uncle in the audio field, I was very happy to have it reading many excellent reviews on the pre revoxes of the time, I did not expect perhaps perfect would be missed ... given the age, but I I immediately start a first test but the device does not switch on, so opening it to a visual check I see nothing, but a check on the 220v line fuses I notice that one was corroded, I clean the connections well and put the fuse back .. now the appliance switches on, all power supply voltages are normal, the nixie display and the search command work perfectly, so I connect the outputs to the amplifier and attach an antenna, perfect audio result on both channels, the only scarce problem ee only mono reception, equipped with services manual that I am attaching, the device is well divided on single cards, the cards that concern the reception are 2-3, A6 IF amplifier and demodulator card, A7 stereo decoder card, maybe even some other card is interested in receiving, I ask for help to you more experienced, I have heard a lot about bad tantalum but it has a control to the capacimetro would be good (welded to the circuit). I replaced C35 on A6 in strong loss with no result, replaced also C20 on A7 but still no stereo reception, but only mono, now I'm a bit perplexed visually and everything ok but I at least hope that some capacitor on the path of the channel is at a loss, I ask you friends of the forum for help and thank you in advance ...

29th Aug 2019, 7:04 pm	#2
Salvatore79 Retired Dormant Member Join Date: May 2019 Location: Termini Imerese, Palermo, Sicily Posts: 8	Re: Revox A720 reception problem only mono no stereo The pdf file is too big, could I link?

29th Aug 2019, 7:54 pm	#3
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: Revox A720 reception problem only mono no stereo Will the PDF compress using a ZIP type application? May be small enough to upload. __________________ Frank

29th Aug 2019, 9:44 pm	#4
Salvatore79 Retired Dormant Member Join Date: May 2019 Location: Termini Imerese, Palermo, Sicily Posts: 8	Re: Revox A720 reception problem only mono no stereo Unfortunately, even converting the file to rar does not give me the possibility to upload it ... too big