ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I've had my Beogram for ~30 years. It has now blown fuses. I've isolated the problem to either the main pc board or the audio pc board. I find it difficult to relate the schematic to the pc board layout. Any ideas as to how to troubleshoot the boards would be welcome. BTW, the audio board is made by Digisonics... apparently not the B&O factory version.
Thanks. Joe
Hi,
Can you post some detailed photos of what you are referring to?
-sonavor
lets see if I can add photos. Can't figure out how to upload photos yet. I'll keep looking.
Joe
just noticed that in my first post I neglected to indicate that my turntable is the Beogram 4004. Sorry about that.
It was in the title though so I figured it was.
There are a couple of ways to put photos in the post.On the edit screen where you compose the text of the post (on the "Compose" tab) there are two other tabs, "Options" and "Preview".The "Options" tab will let you Add/Update a file. It pops up a dialog so you can browse to the photo and upload it. It will then put that one photo in your post. Be aware that there is a limit on the size of the image file.
The other way takes a little more setup but it allows you to post multiple photos in one post. It uses the little filmstrip icon on the edit toolbar where you type in your post. However, before you can use the filmstrip to insert media you should upload your media (photo files) to your Beoworld profile. You do that by clicking on your Beoworld Member Name link. Then on your Profile page scroll down where you can see the "My Files" section on the right side of the screen. From there click on the "view all files" link. It changes the screen to your-user-name Files. There are controls on that screen to choose (browse) for a local file and add it. You can also create folders to organize your photos. It takes a little getting used to but isn't difficult to get the hang of.Once you have added files to the My Files section you can go back to your forum post and use the filmstrip icon to navigate and select the files you want to put in your post.Hope that helps.-sonavor
Make sure your pics are smaller than 1000 Kbs
To upload pics to your files and keep them on the forum server, for later use, when making a longer thread, do like this
Click view all files, way down in the right corner
If you uploads pics without making folders, you will get all your pics in "my files". If you make folders, you can only make 9-10 folders, if more folders, you wont be able to open them when posting. And remember, write folder names like when you had a Comodore or PS1 computer, Nospaces in Folder name.
After adding a folder, you get this pane, open the newly added folder.
To add pics to folder, click browse, find the pic in your computer, click open or double click, then click add file.
After clicking Add File, your pane should look like this.
Now continue to Browse, select pic, Add File to this folder, or make one more folder and do the same there.
How to post the pics in your Thread or Answer, I will post in another page, its a Looong story, as we are working with bad or Outdated server software.
Collecting Vintage B&O is not a hobby, its a lifestyle.
Pics has to be less than 1000 Kbs
Start a new thread, or post an answer in a thread
Every time you insert a pick, you will have to run the whole click,click, and every time you insert a pic, the pane will reset to the starting point and you will have to scroll down to the last inserted pic.
It easier to just write the text, insert pic from options, post, answer to thread and insert one more pic and so on.
This way is a waste of time.
Sorry to say... I have uploaded three pics to the site but I can't get them to go here.
When I click on the film strip I press "Joe's Files" and it says "loading..." but nothing happens. Am I not waiting long enough?
Yes, it must be taking a long time to load where you are.
I can't go to your profile and see the three photos you uploaded there. They should appear and allow you to select them for placing on post.
Can you take a picture of the component side of your output board?
Also, can you post some higher resolution versions of the photos? I can't zoom in close enough to see details very clearly. Uploading the files like you did lets you put larger size photos.
Martin
Thx Dillon for moving the photos. I now have 4 pics in the beo4004 folder and want to upload one more (audio component). Using the film strip I only get the "loading... but nothing happens. Can you tell me how to move the files from my folder so I can post?
Thx.
Just use the "insert media" button when you write a reply - just as Søren Mexico explains above.If that doesn't work, I have no idea what's wrong.It's the modern world. The younger generation seem to prefer things that are unnecessarily complicated and only almost work - sometimes.
Looks to me like a RIAA module, that also holds the filter capacitor.
Dillen: Just use the "insert media" button when you write a reply.If that doesn't work, I have no idea what's wrong.It's the modern world. The younger generation likes things that almost work. Looks to me like a RIAA module, that also holds the filter capacitor. Martin
Just use the "insert media" button when you write a reply.If that doesn't work, I have no idea what's wrong.It's the modern world. The younger generation likes things that almost work.
Only if “theres an app for it” 😄
Dillen: Looks to me like a RIAA module, that also holds the filter capacitor. Martin
Now that we can see the board what is the history?
You mentioned that you have had it for about thirty years. I take it that it had this modification to it when you received it?When you used the BG4004 did you plug it into the Phono input of your amplifier or to something like Auxiliary or a Tape input?What kind of audio connections does it have? The 5 or 7 pin DIN or two RCA plugs?
My original issue was overheating the power supply diodes then blowing fuses. When the upper left socket on the audio board is unplugged, the short stops. unplugging the lower left socket has no effect. Thus, I suspect something on the audio board. With the socket unplugged the switches and transport are working.
Only 4 wires run from the main board to the audio board, two of which are ground. I planned to start looking at components that trace from the two non-ground leads.
I acquired the 4004 from a family member about 30 years ago (he has since passed) who purchased it from a stereo shop in SF and it has worked flawlessly until about a month ago. I guessing he changed the board to the Digisonics board since most likely its not an original Beo 4004 component.
The TT was plugged into the RCA phono inputs on my MacIntosh Preamp.
Hope this story helps. Any ideas are appreciated.
Interesting. So if the turntable was connected to the MacIntosh Phono input that preamp would be handling the RIAA part of the signal processing.That replacement board houses the big filter capacitors for the turntable power so that is interesting. The rest of it I can't tell. The original BG4004 had the phono signal muting relay and associated connectors (which yours also has). The other part of the original board was a circuit for remote control functionality with the Beomaster 2400.
Regardless of the modification I would recommend replacing the electrolytic and tantalum capacitors with new ones as a first step. See if that solves your main problem. If you can find anyone from the old stereo shop they might have some notes on the Digisonics board. That would be helpful and interesting to see.Searching for current Digisonics references I only find information on a medical related company.
If you are up to it I would like to see what the schematic is for the components on the Digisonics BG4004 replacement board. -sonavor
I did write to the Digisonics company to see if they did this sort of things in the "old days" but no reply so far. I have looked for a schematic for the Digisonics board but no luck.
If I could find an original version of that board I'd buy it and install it... so far nothing shows up.
Assuming you have 4004 schematics (I can post one if you don't) diagram 2 does show below the dashed lines the same traces on the Digisonics as on the Beogram schematic. the red and blue leads from the main board go to pin 1 and 8 of the upper left socket and converge near the bottom of the diagram with the transistor coupling the two circuits. I thought about changing that transistor (I have lots of them).
I will take your advise and change out those caps and see what happens. I didn't see those caps noted in diagram 1 schematic for the 4004 so I assumed the caps were for circuits on the Digisonics board.
I think that stereo shop is long gone.
Thanks so much for helping me diagnose this project.
Hi Joe,
I sent you some links to a couple of in depth Beogram 4004 restorations via email.I will repeat them here for convenience -
Beogram 4004 A
Beogram 4004 B
Beogram 4004 CThe first two links are ones I did last Winter (December 2018/February 2019 - for the same owner).The third link is one beolover did last Winter (February of 2019) .I might have a spare Beogram 4004 output board but I need to check. I think it would be a good idea to return the Beogram back to its original state. I would be interested in what the idea was behind the modified board someone installed 30 years ago. It seems rather extreme. Why did they move the reservoir capacitor from its original location? You will need to study and figure out what or if any drastic wiring mods were made so you can return to the original board.Your photos don't cover the Beogram 4004 AC connector. In the original configuration there is a P3 connector (4 pins) on the left side of the turntable cabinet where the transformer AC comes in to the main board and also connects to a single 4000uF capacitor. It appears that the modified output board has the power supply for your Beogram. Some sort of Teledyne Power Brick and two reservoir capacitors. Is the original Beogram 4004 transformer still in your Beogram or does the AC cable go right to that Teledyne device? You can compare the inside of your Beogram 4004 to the links I sent you.
Cripes!Someone went to an awful lot of trouble doing this conversion?
I don't know what the Teledyne thingy is,but it seems to be a device that converts a single polarity supply(30v in this case ?)into a +5/-5 (?)supply for the opamps employed here?
The printed circuit seems to have suffered distress as though excess current has been drawn,and it looks as though someone has gone over the board with a big soldering iron,as.there seem to be blobs of solder and even a piece of wire bridging circuit tracks,although the definition of the pic (and my eyesight!)aren't great!!!
With the pcb out of the machine,measure the resistance across either of the two large capacitors first,then check the two small black diodes in each pre-amp supply.If any reading's are low ohms,you have found the problem.
The chips seem to plug in too,so you can take them out one at time until the short clears,then you have found the culprit!
Good luck with it.I imagine that it sounded quite good when working?
Nick
Hi Sonavor,
Thanks for the links... I am willing to do much of the restoration but I wanted to at least get past this shorting thing. I'm hoping you find the 4004 outboard board... will dramatically shorten my repair efforts then on to restoration.
I do have a pic I'll try to post (not having much luck with that process) that shows that the main Power source and rectifier diodes are the usual place for the TT...on the left rear side of the chassis. The big cap is near the entry to the main board. The two large caps on the preamp board are filter caps for the Teledyne DC to DC converter. Thus the main board is unmodified standard issue.
Did check some voltages and the main board is putting 29vdc into pin 1 and 2 of the plug for the Preamp socket. Not sure what the preamp board is looking for in that pin. Additionally that pin goes to resistor 8R1 that s/b 100k ohms but measures only 1k ohms... an "in-circuit" variance? Don't know.
And the main board is putting 9vdc into pin 8 of the preamp socket... but, if I read schematic 2 correctly, it may be looking for 21vdc.
A somewhat unrelated to the short issue I noticed that the light that detects the tonearm positioning may be burned out. is that bulb AC or DC?
BTW, Nick gave some interesting inputs. Did pull each of the IC's one at a time and all had no effect on the short. I unsoldered one side of the big caps but no impact. Did not check the diodes yet.
Does Beolover sell parts?
Here is the Power Supply portion of the TT
Well, as usual...I can get the pic to my Folder but can't get it to download with the film strip icon.
Yes Beolover does sell his parts. It is puzzling and interesting what the purpose of that replacement board is for. Like Nick figured, the Teledyne power device is to provide a power source for the ICs. If you still had to run the phono plug of the Beogram 4004 to the Phono input of the MacIntosh preamp then it would handle the raw audio directly from the phono cartridge. That leaves me still wondering what the added circuit with the ICs does. Are those ICs all OpAmp devices?Back to your problem though...I would seem as if the added board isn't causing your blown fuse problem. It also seems like you should just be able to replace the modded output board with an original and the Beogram 4004 will be back to normal.
I was able to see your latest photo in your files. When you access those using the filmstrip icon tool you need to make sure and navigate into your beo4004 folder to get to those pictures. Your transformer, reservoir capacitor and power cable to the main board all look like they should in a Beogram 4004.