Jester Posted January 25 Posted January 25 Hi all, First time post, hopefully this is in the right forum. I have a Studer a764 FM Tuner. The unit will not change from the preset frequency 97.1MHz. I read in the service manual: https://www.worldradiohistory.com/Archive-Catalogs/Studer/Studer-A764-Op-Serv.pdf the following: In order to prevent inadvertent actuation of the control keys, the operation of tuner can be completely disabled by means or a jumper. Factory setting: Jumper not set, ie. the tuner is fully operable Does anyone know where this jumper is and how to return it to factory setting?
audiofeline Posted January 26 Posted January 26 (edited) Welcome to SNA Jesse. What page of the manual are you quoting? Have you taken the lid off and looked for jumpers on the circuit boards? If you find a jumper on a board there may be an annotation indicating it's purpose, or it will identify a board to explore in the service manual. I note that there is the service manual available on ebay in the US, if you want an original. Being a professional model, the manual format is a big red binder - looks impressive! For others looking at the manual, English starts p.89 of the pdf. Edited January 26 by audiofeline
mbz Posted January 26 Posted January 26 (edited) page 132, also note reference to DIN socket, see also bottom of page 133 which shows somewhat logical connection, maybe post several hi-res pix of the power supply unit/board, I assume there is no jumper connected to the DIN. I'm guessing that the tuner is locked and does not respond to any keys and you are thinking/"guessing" that it's because of this jumper, consider that it could be a fault, there may be a microswitch to detect when front cover is closed... switch failed? page 156 7.5.3 Operating Modes provides further explaination, appears that you should be able to always adjust the frequency. Edited January 26 by mbz pg 156
Jester Posted January 28 Author Posted January 28 Thanks Rob and Mike, Page 95, (E 1/6, section 1.4, point 4). It is referring to the button that opens the front panel and seems to mention the jumper in passing. There is a jumper on two of the top most boards, see red circles pic 1. Mike, I saw that reference to the DIN socket. I think that this section is discussing how the remote interacts with the jumper settings. I suppose it is possible that the jumper on the power supply (right hand) board is A11, as the DIN socket for the remote is on that board. It would also make sense that this jumper was relatively easy to access. I will lift that board and see what labeling there is underneath. The op manual is pretty hard to follow and I can't see any further reference to A11. I'll try to print it out so that I can read it more thoroughly. Thanks for your help so far. Jess 2
surprisetech Posted January 29 Posted January 29 That's an impressive tuner! I assume this one was used as a broadcast monitor in a Radio Station. Coincidentally, 97.1 is the frequency for our local 3MDR community station in the Dandenong Ranges, but I doubt they would have ever had a monitor of this calibre! Looking at the block diagrams and schematics, while "A11" is associated with uProcessor B1, the jumper is shown as being on the power supply unit to make it accessible. Tracing the circuit, it looks like the jumper you have circled behind the DIN sockets (JP1/P4) is it. The jumper on the MPX/SCA board is definitely not it. I just had a quick look on the TIC website, but this tuner is not there under the Studer brand. There was mention though that Studer & Revox Tuners were often the same, so I checked the Revox listings and the photo of the Revox B260 looks very much like your Studer A764. Studer A764 is the 'pro' version for use in applications like broadcast monitoring. https://www.fmtunerinfo.com/reviewsO-R.html#revox Hifi Engine has manuals for the Revox B260, but the service manual is only in German and may not include the feature to disable the controls. I'll be following this thread with interest.
audiofeline Posted January 29 Posted January 29 (edited) If you identify the boards with the jumpers you should be able to identify the function of the board (via the manual), and possibly find the jumper on the schematic. If the jumper doesn't affect the power, you could be safe removing it to see if it unlocks your problem. Disclaimer: I'm not a tech, so if anyone more knowledgeable than me thinks this is unwise please correct me! Out of interest, did you get the remote with it? Edited January 29 by audiofeline 1
surprisetech Posted January 29 Posted January 29 16 hours ago, audiofeline said: If you identify the boards with the jumpers you should be able to identify the function of the board (via the manual), and possibly find the jumper on the schematic. If the jumper doesn't affect the power, you could be safe removing it to see if it unlocks your problem. Disclaimer: I'm not a tech, so if anyone more knowledgeable than me thinks this is unwise please correct me! Out of interest, did you get the remote with it? The 'A11' jumper (JP1/P4 on the Power Supply board), only changes a logic level into an I/O port on the microprocessor. Safest way to test its function would be to turn off the tuner & disconnect the power cord. Change the jumper setting. Re-apply power, turn on & test.
Jester Posted January 30 Author Posted January 30 Hi Rob, No I didn't get a remote with it. surprisetech, What setting would you suggest I try, jumper open (removed) or in the other closed position?
audiofeline Posted January 30 Posted January 30 Remove your best choice of jumper first, leave the other as is. Put the cover back on (as it seems to lock the operation when it's off), and see if removing that jumper made a difference. It it doesn't fix the problem, put it back, remove the other one, reassemble and try again. When trouble-shooting, only change one thing at a time, otherwise you don't know what's influencing any change that might occur. Good luck!
surprisetech Posted January 30 Posted January 30 58 minutes ago, Jester said: Hi Rob, No I didn't get a remote with it. surprisetech, What setting would you suggest I try, jumper open (removed) or in the other closed position? Just try the other position first. If there is no change, try with the jumper removed completely. If still no change, then put it back to where it was originally, and we'll try and think of something else to try. Use the procedure i suggested above with each change. With these types of settings it's often the case that the microprocessor only checks the setting on startup.
Jester Posted February 2 Author Posted February 2 OK, plot thickens... I tried the other position first and tried to scan stations. The frequency did change the first time I pressed the scan button, (perhaps a coincidence, see below). After that no other changes. Tried the open position, no response. Other things to note: -the unit will not power down as described in the manual by pressing and holding the power button. -there is no sound output, perhaps because the unit is muted. -I noticed that there are two lights on indicating "Remote" and "Mute" It seems as if the unit is expecting control from a remote, but not getting any input and preventing any other controls from working. Was the initial change coincidental with me pressing the scan button and it would have returned to a factory setting regardless? Thoughts?
audiofeline Posted February 2 Posted February 2 Interesting. The "mute" light would be the reason you don't have output. First, turn it off at the power point, wait a few seconds before powering on again, it might benefit from a reset. Have you returned the jumper to the previous/original position?
Jester Posted February 2 Author Posted February 2 Yes, jumper is back in original position. Power off and restart for each change. 1
surprisetech Posted February 3 Posted February 3 18 hours ago, Jester said: OK, plot thickens... I tried the other position first and tried to scan stations. The frequency did change the first time I pressed the scan button, (perhaps a coincidence, see below). After that no other changes. Tried the open position, no response. Other things to note: -the unit will not power down as described in the manual by pressing and holding the power button. -there is no sound output, perhaps because the unit is muted. -I noticed that there are two lights on indicating "Remote" and "Mute" It seems as if the unit is expecting control from a remote, but not getting any input and preventing any other controls from working. Was the initial change coincidental with me pressing the scan button and it would have returned to a factory setting regardless? Thoughts? Not sure what else to suggest. I wonder if the jumper setting has been hard-wired on the underside of the PCB. If you can access the underside of the board it might be worth checking if the option has been permanently set with a wire link or a solder bridge. It might be worth posting a query on the FM Tuners Group. There are already a number of threads there on the A764. I've had some good responses in the past when posting questions on less common tuners. https://fmtuners.groups.io/g/main 1
Jester Posted February 3 Author Posted February 3 Thanks for your suggestions. Will post if I find a solution. 1
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