Studer A807 Disassembly help - UK Vintage Radio Repair and Restoration Discussion Forum

allobytw · 15th Nov 2016, 3:31 pm

Hi, hello everyone. A friend of mine has asked me to look at a Studer A807, he thinks it needs new belts. I have been trying to remove the top panel, but it seems like its got a screw under bottom right that I can't see or access. Could anyone help with advice, or a diagram on disassembly. I think its a Mk1.
Thanks in advance, Alby.

Ted Kendall · 15th Nov 2016, 6:49 pm

No belts, for a start. What exactly is the matter with it?

allobytw · 15th Nov 2016, 8:24 pm

Hi thanks for reply when I was asked to look at it he said it needed new belts ,because I am not familiar with these I never questioned him .I will try and contact him to find exact problem and get back to you.But I would still like instructions for disassembly to clean it etc.

allobytw · 15th Nov 2016, 8:41 pm

I have spoken to my mate he said It switches on but when you press play nothing happens,up till now he said it has been a great machine running with no problems.

Ted Kendall · 15th Nov 2016, 11:12 pm

First thing to check on these is the power rails, which are protected by internal fuses. Best also to download the service manual from the Studer site - these are complex beasties and a pain to work on because they aren't modular, so best to have the maps by you before you delve too deeply.

allobytw · 16th Nov 2016, 1:17 pm

Hi thanks for advice.

Will it show me how to remove the top in THE service manual? What manual is it?

Ted Kendall · 16th Nov 2016, 2:01 pm

Google Studer A807 Service Manual and you will see a link to the manual in pdf form from the Studer ftp site.

allobytw · 16th Nov 2016, 4:46 pm

Ok thanks will do that I will let you know how I get on.

allobytw · 16th Nov 2016, 10:49 pm

I took your advice and checked the fuses 2 are blown a T2 and a T4 I. have ordered some from RS ,is this common with these machines.

vidjoman · 16th Nov 2016, 10:55 pm

Well, fuses blow for a reason. In this or other machines. Before fitting you should try to find out why they blew. First find out what part of the circuit they protect then try and find the reason.

Michael Maurice · 16th Nov 2016, 11:30 pm

Eckoing Vidjoman and Ted's posts, if there is a short somewhere you could do considerable damage.

Looking at the manual, F4 is for the 20V supply, F2 is for the 50V supply

Radio Wrangler · 17th Nov 2016, 8:13 am

Fuses have a wearout mechanism. They age depending on time and current. The rated current is the value of continuous current which will cause them to blow in 1000 hours as the mean of a large number of samples. Reduce the current, and the time to blow increases fairly rapidly. You need quite a large percentage over-current to pop one rapidly. Fuses which regularly handle large current surges, but not big enough for an immediate blow, exhibit shortened lifetimes.

Studer knew what they were doing and picked fuse values wisely. But A807 machines are old now and anyone who could justify their new price had some serious paying work for them to do.

It is quite possible that the fuse died of natural causes through age and acceptable currents.

It is also possible that something down-stream of it has failed, like a decoupling capacitor going short-circuit, and the fuse did its job.

Playing safe involves testing the circuitry which the fuse protects before replacing the fuse and powering it up again. Some people say that whatever damage there is downstream has likely already been done and there won't be much more risk in trying a replacement fuse of the exact right rating. These people are not always right. It's a gamble. How lucky do you feel? With a rare and desirable machine where spares aren't always available, I wouldn't gamble.

David

allobytw · 17th Nov 2016, 3:01 pm

Thanks I really appreciate all your help and advice I will look for any obvious damage and test the 2 supplys before I replace fuses.Will keep you updated.

allobytw · 18th Nov 2016, 7:17 pm

I checked each line and nothing was blown or faulty so I replaced fuses and the machine seems to be working normally although I have not got any tapes to fully test it ,the play reel/rewind have life again.I am now waiting for tapes to try fully so again thanks to members who have guided me and I will update I can test fully.

15th Nov 2016, 3:31 pm	#1
allobytw Retired Dormant Member Join Date: Nov 2016 Location: Liverpool, Merseyside, UK. Posts: 8	Studer A807 Disassembly help Hi, hello everyone. A friend of mine has asked me to look at a Studer A807, he thinks it needs new belts. I have been trying to remove the top panel, but it seems like its got a screw under bottom right that I can't see or access. Could anyone help with advice, or a diagram on disassembly. I think its a Mk1. Thanks in advance, Alby.

15th Nov 2016, 6:49 pm	#2
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,670	Re: Studer A807 Disassembly help No belts, for a start. What exactly is the matter with it?

15th Nov 2016, 8:24 pm	#3
allobytw Retired Dormant Member Join Date: Nov 2016 Location: Liverpool, Merseyside, UK. Posts: 8	Re: Studer A807 Disassembly help Hi thanks for reply when I was asked to look at it he said it needed new belts ,because I am not familiar with these I never questioned him .I will try and contact him to find exact problem and get back to you.But I would still like instructions for disassembly to clean it etc.

15th Nov 2016, 8:41 pm	#4
allobytw Retired Dormant Member Join Date: Nov 2016 Location: Liverpool, Merseyside, UK. Posts: 8	Re: Studer A807 Disassembly help I have spoken to my mate he said It switches on but when you press play nothing happens,up till now he said it has been a great machine running with no problems.

15th Nov 2016, 11:12 pm	#5
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,670	Re: Studer A807 Disassembly help First thing to check on these is the power rails, which are protected by internal fuses. Best also to download the service manual from the Studer site - these are complex beasties and a pain to work on because they aren't modular, so best to have the maps by you before you delve too deeply.

16th Nov 2016, 1:17 pm	#6
allobytw Retired Dormant Member Join Date: Nov 2016 Location: Liverpool, Merseyside, UK. Posts: 8	Re: Studer A807 Disassembly help Hi thanks for advice. Will it show me how to remove the top in THE service manual? What manual is it?

16th Nov 2016, 2:01 pm	#7
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,670	Re: Studer A807 Disassembly help Google Studer A807 Service Manual and you will see a link to the manual in pdf form from the Studer ftp site.

16th Nov 2016, 4:46 pm	#8
allobytw Retired Dormant Member Join Date: Nov 2016 Location: Liverpool, Merseyside, UK. Posts: 8	Re: Studer A807 Disassembly help Ok thanks will do that I will let you know how I get on.

16th Nov 2016, 10:49 pm	#9
allobytw Retired Dormant Member Join Date: Nov 2016 Location: Liverpool, Merseyside, UK. Posts: 8	Re: Studer A807 Disassembly help I took your advice and checked the fuses 2 are blown a T2 and a T4 I. have ordered some from RS ,is this common with these machines.

16th Nov 2016, 10:55 pm	#10
vidjoman Dekatron Join Date: Jun 2013 Location: East Sussex, UK. Posts: 3,326	Re: Studer A807 Disassembly help Well, fuses blow for a reason. In this or other machines. Before fitting you should try to find out why they blew. First find out what part of the circuit they protect then try and find the reason. Last edited by vidjoman; 16th Nov 2016 at 10:55 pm. Reason: Spell checker

16th Nov 2016, 11:30 pm	#11
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,224	Re: Studer A807 Disassembly help Eckoing Vidjoman and Ted's posts, if there is a short somewhere you could do considerable damage. Looking at the manual, F4 is for the 20V supply, F2 is for the 50V supply __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

17th Nov 2016, 8:13 am	#12
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,868	Re: Studer A807 Disassembly help Fuses have a wearout mechanism. They age depending on time and current. The rated current is the value of continuous current which will cause them to blow in 1000 hours as the mean of a large number of samples. Reduce the current, and the time to blow increases fairly rapidly. You need quite a large percentage over-current to pop one rapidly. Fuses which regularly handle large current surges, but not big enough for an immediate blow, exhibit shortened lifetimes. Studer knew what they were doing and picked fuse values wisely. But A807 machines are old now and anyone who could justify their new price had some serious paying work for them to do. It is quite possible that the fuse died of natural causes through age and acceptable currents. It is also possible that something down-stream of it has failed, like a decoupling capacitor going short-circuit, and the fuse did its job. Playing safe involves testing the circuitry which the fuse protects before replacing the fuse and powering it up again. Some people say that whatever damage there is downstream has likely already been done and there won't be much more risk in trying a replacement fuse of the exact right rating. These people are not always right. It's a gamble. How lucky do you feel? With a rare and desirable machine where spares aren't always available, I wouldn't gamble. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

17th Nov 2016, 3:01 pm	#13
allobytw Retired Dormant Member Join Date: Nov 2016 Location: Liverpool, Merseyside, UK. Posts: 8	Re: Studer A807 Disassembly help Thanks I really appreciate all your help and advice I will look for any obvious damage and test the 2 supplys before I replace fuses.Will keep you updated.

18th Nov 2016, 7:17 pm	#14
allobytw Retired Dormant Member Join Date: Nov 2016 Location: Liverpool, Merseyside, UK. Posts: 8	Re: Studer A807 Disassembly help I checked each line and nothing was blown or faulty so I replaced fuses and the machine seems to be working normally although I have not got any tapes to fully test it ,the play reel/rewind have life again.I am now waiting for tapes to try fully so again thanks to members who have guided me and I will update I can test fully.