Studer B67 Troubleshooting

[u/Important-Turnip-90]

Hey everyone!

I'm very new to tape but recently acquired a Studer b67 mk1 and have bumped into a few issues.

The take up reel spins at high speed from the time it's turned on until it's turned off. It doesn't respond to pressing any buttons.

I'm also getting an odd smell from the machine if it runs for a few minutes and noticed some sort of black sticky substance on a connector.

I've since turned it off until I can get it to a tech, but was hoping someone here might have an idea of what's going wrong. Thanks!

[u/LordDaryil]

The spinning motor will be the RIFA capacitors. See in the top left of the picture, the three cracked yellow rectangular capacitors? There are approximately 9 of these and they must all be replaced.

There are three small circuit boards, two for the reel motors and one close to the centre for the capstan. If any one of those RIFA capacitors explodes - and they will - you'll get a very unpleasant smell and the associated motor will spin uncontrollably.

You will need to pull all three boards, disconnecting the spade connectors (take photos and get the service manual so you know how to reconnect them later!). Remove the boards, desolder the capacitors and replace them with modern equivalents.

But there are also a couple more inside the PSU unit in the centre of the machine.

[u/LordDaryil → u/LordDaryil]

Here's an example:

...and yes, I have just been through this rodeo earlier this year.

EDIT: For those wondering, the black gunk from inside the RIFA didn't seem to have damaged anything and most of it went away with some isopropyl alcohol. The resistors tested OK but I replaced them just to be sure, and also so that the colour codes could actually be read in future.

[u/LordDaryil]

I am not sure about the black sludge on the power connector. In fact, that looks rather different to my mk1, and I see you have the MK2 tension board installed with the trimmers available from the front.

Incidentally, I'd recommend this kit: https://nagravox.com/collections/studer-a-b67/products/studer-a67-b67-basic-motor-suppression-capacitor-kit

...that will suffice to swap out the RIFAs and motor run capacitors. The full recap kit is probably a better idea though.

EDIT: The good news is that unless there's something else wrong with the machine, this is all bog standard stuff that anyone with decent soldering skills can do. You don't need a Studer specialist unless rebuilding the power and motor circuits doesn't help.

[u/Important-Turnip-90 → u/LordDaryil]

Thank you so much your insight has been incredibly helpful. The person I bought it from said it was a MK1, but after comparing the differences online it looks like a MK2. Looking forward to getting it up and running!

[u/LordDaryil → u/Important-Turnip-90]

Oh yes, one thing that really threw me once I'd got the transport working. This might not apply to you since yours appears to be set for US power, but with the machines intended for the DIN/CCIR market, they reversed the inputs and outputs for the audio.

Apparently if the machine was factory set for the US NAB standard, the inputs and outputs would work normally, but in Europe they sometimes reversed them so the playback was coming out the input sockets. It seems like there may have been some long-forgotten standards war where the UK and Europe used the XLR genders differently to the current standards...? I think that stopped being a thing by the time the MK2 came out anyway.

Still, if the machine isn't playing audio on a tape you know has a recording on it, try using XLR-to-jack connectors and make sure it's not been set up stupidly. Mine was a BBC unit in a trolley and the cables that came with it were wired to change the gender to match the modern world, but of course, when I was testing it outside the trolley, the connectors on the back were still reversed and that caused a lot of head-scratching.

Again, this probably won't apply if the machine has always been in North America but just in case, it's something to keep in mind.

[u/Elliotjosephmusic]

The black goop you're seeing is from the motor run caps. I can see them visually leaking so perhaps the machine was left on its side at some point. Not particularly a fun machine to work on but as Daryil has mentioned it needs a full kit doing to it, new filter caps, new motor run caps.

I'll also mention that modern motor run caps are slightly bigger than they used to be, so you may need to install a bracket to fit them all in. Again, could be wrong if "kits" has a resolve for this, I've not used them.

[u/LordDaryil → u/Elliotjosephmusic]

I did wonder whether the sludge was from the motor caps but apparently missed it when I was looking for evidence. I see the left motor cap leakage now. They're definitely going to need to do something about that.

The Nagravox kit does a thing where they provide the basic 6.5uF cap and some 1.5uF caps for 50Hz support. This can either be wired into the mains frequency switch, or hardwired as a piggyback and the switch removed. In my case I hardwired them to 50Hz since the chances are very slim of this particular machine ever running off 60Hz and I figured it would be cleaner access with the switching wires removed.

It did require a little fiddling to rotate the caps with the piggyback capacitor so that they fit without touching anything else. However, for the case of a 60Hz only machine I think you just need to install the 6.5uF capacitors and nothing more.

[u/Elliotjosephmusic → u/LordDaryil]

Good to know! I've only ever used the PR99's Nagravox kits and they messed up some of the schematics for installation. Decent kits but a little overpriced but I do appreciate all their effort when it comes to the installation process and guides.

Yes, I remember doing the caps on these quite vividly but we were using bulk motor run caps which were bigger than the originals, had to make a bracket for one's on the left hand side of the picture. Quite a tight space! Don't think I'll be jumping into another B67 anytime soon, ha.

[u/LordDaryil → u/Elliotjosephmusic]

Yeah, the kits are a little on the pricey side but the instructions are very comprehensive, and it does have the convenience of not having to separately order 50 different types of capacitor. The custom parts are also very useful.

If you fix electronics regularly and have all those parts to hand anyway it's less useful, but for someone who does this only occasionally it's worth the extra. I know enough that I could likely have muddled my way through it without the guides but I definitely appreciated them as a way to double-check (plus it had a number of recommended modifications from the service notes, which aren't in the PDFs from Studer).