Tascam 48 Amp Cards

Things are coming together slowly, equipment-wise. I wanted to use my 1/2″ 8-track, a Tascam 48-OB, so I hooked it up to the mixer and went at it. Something was really wrong, though. I recorded something onto track 1 of the tape, and on playback, the VU meter on the deck looked OK but I was getting hardly any signal on my mixer. After running through the cabling and checking everything on the mixer, the cause of the problem appeared to be in the tape deck, but I had no idea what it was.

I posted a thread on homerecording.com and a few people suggested that it might be the relays on the amplifier cards. To be specific, there’s two relays on each amplifier card that control signal output. The 48 runs at either +4dB or -10dB, and these relays switch between the two sets of inputs and outputs. When they fail, they’ll often they fail simultanously, breaking on multiple channels. This made sense, as the problem soon spread to 4 of the 8 channels on the deck.

To make sure that its was the relays, I plugged the +4dB balanced outputs into a firewire interface and played a MRL testing/calibration tape several times, going from channel to channel each time. They all worked. This confirmed that it was indeed a problem with bad/dead relays.

After asking several more questions, I found out that the bad relays were the ones labeled “K003″ on the amplifier card. These relays are used when using the deck’s -10dB unbalanced outputs. The stock relay is an NEC component that is no longer manufactured, but a company called Hamlin makes a perfect replacement. It’s the HE721A2400, and it can be found at DigiKey for cheap.

Hamlin HE721A2400 Relays

Replacing the relays isn’t difficult but it requires some basic soldering skills. You will need a solder sucker; most decent electronics or hobby supply shops sell a basic model for $15-$20. Knowing how to use it is also important: I didn’t know how to use one and carelessly assumed that I could figure it out, and ended up damaging one of the cards (I repaired the damage, though). To remove a component from a circuit board, apply the soldering iron tip to the lead of the component on the “top” side of the board, while applying the solder sucker tip to the bottom of the lead on the “bottom” side of the board. When the solder appears to have melted, click the solder sucker and the molten solder gets sucked out of the drilled PCB hole and into the sucker. I wish I had a picture to demonstrate this, but reread the last sentence and ask any questions if it’s unclear.

After removing all of the K003 relays, I soldered IC sockets to the holes where the relays had been. I did this in case the relays need to be replaced in the future… saving myself or someone else some work. The relays snapped into the sockets easily. Here’s a picture of one of the replacement relays, in its socket:

Closeup of New Relay

I put the cards back into the deck, put the MRL tape on again, and everything worked just fine. I was so relieved to have it working again, and I was proud to have fixed it myself… with a lot of help, of course.

Notes:

• The Tascam 42, 44, and 48 share the same amp card design. This repair will work for any of these models.
• A full calibration should be done on the deck after replacing the relays. The relay’s performance seems to degrade over a period of weeks before completely breaking, and it might have been compensated for in different ways as it worsened over time. Bringing the deck to a solid, accurate state is definitely recommended.

It’s a total mess right now, because a lot of stuff is being repaired.

Studio Inventory

Mixers:

• Tascam M-520 20x8x4 mixer
• Tascam M-30 8x4x2 mixer in pieces, awaiting restoration
• Tascam M-216 16x4x2 mixer in pieces, awaiting restoration

Tape Recorders:

• Tascam 34b 1/4″ 4-track (x2) one functioning, one disassembled for complete restoration
• Tascam 48 1/2″ 8-track needs relay replacements on all eight channels, pending op-amp and capacitor replacement/upgrade
• Otari MX5050 MKIII-2 1/4″ 2-track
• TEAC X10-R 1/4″ 4-track (quarter track stereo) the most disassembled of all my tape decks, currently on life support
• Tascam 302MkII cassette deck
• Marantz PMD 430 cassette field recorder

Noise Reduction for Tape Recorders:

• dbx 150x (x6)
• Tascam DX-4D (x2)

Monitors:

• Yamaha HS-50M (x2)

Outboard:

• dbx 166xl two-channel compressor/limiter (x2)
• ART MPA Gold mic/line preamp (x2)
• ART Pro Verb reverb unit

Sound Sources, Miscellaneous Input/Output:

• TEAC AG-790 stereo receiver
• Audio-Technica AT-PL120 turntable
• Toshiba Hi-Fi VHS VCR
• Alesis io26 firewire interface

Microphones:

• Shure SM57 (x2)
• Marshall MXL-604 small diaphragm condenser (x2)
• Rode NT4 small diaphragm condenser, XY stereo pair
• Rode K2 large diaphragm condenser
• Naiant X-S miniature small diaphragm condenser, omnidirectional (x2)
• Homemade piezo contact microphone (x4)

Patchbays:

• Tascam PB-32W
• TEAC PB-64 (x4)
• Coming soon: DIY homemade normaling patchbay for accessory send/receive jacks on my M-520

Photos

TEAC X-10R, Otari MX5050 MkIII-2

Tascam M-520

Tascam 48-OB

Tascam 34b, In Pieces, Awaiting Restoration

Tascam 34b

Tape Shelf

Back of Patchbay

Photo from a show, July 2008

Patchbays

Honey the Cat, an essential element of the studio

Cable Heap

Behind the Tascam M-520

Behind the Console

Behind the Tascam 48-OB

Reel motor from Tascam 34b

Demo Clip Demo Clip Demo Clip:

It’s been nearly two weeks since I last wrote. I’m a bit bogged down in projects right now and I haven’t had much opportunity to make music.

A few technical issues have sprung up and I’m taking care of them as best I can. I was really hoping that I’d be out of the woods by now, equipment-wise, but it looks like I’m not there yet.

After eliminating most of the hums and buzzes from my studio, I hooked up my Tascam 48 eight track machine to the console and started recording. On playback, however, I noticed that four of the eight channels were producing weak signals. The needles on the VU meters looked right, and it wasn’t an issue with the mixing console. Something is happening in the amplification stage in the tape deck.

I opened up the machine and removed the amp cards to clean and inspect them. After putting them back in, the problem was still there and it appeared to follow the cards. That means that there’s something wrong with those individual amp cards. Maybe. I’m waiting to pick up a calibration tape, and I’ll start from the top and work to the bottom to find the problem and (hopefully) its solution.

Also, with my secondary Tascam 34b quarter-inch four track machine, I noticed problems with the reel motors on playback, fast forward, and rewind. When a tape is loaded, the motors will run at normal speed and then grind to a halt. So, I opened the deck, removed the motors, and gave them a full cleaning. I will also replace the bearings once I find a bearing puller to remove the old ones. I also replaced the belt, which I was going to do anyway.

Guts from Tascam 34b reel motor

This doesn’t touch on the issues that I’ve had with other equipment, but I should fix these two things before I move on to other projects. The eight-track is my primary multitrack, and the four-track machine will be very important for editing loops and for doing echo and delay. I kind of need them to work. You know.

- – -

I had a loop sitting on the bench, which I left there after I discovered that my eight track was broken. I put it on the working four-track deck and recorded it into Audacity. The original sound is a guitar chord, and I cut off the attack and made a loop from the remainder. This is one of my favorite techniques because the sounds that it produces are very glassy, and often sound like chimes. This was recorded in my bedroom, and I purposely EQed it to bring out the room sounds: my dehumidifier, street traffic, and general environmental white noise. It’s great as a demo, and I will eventually do it again in a proper studio for a more polished result.

- – -

I have a couple of building and design projects on my plate, too. I’m designing a loft bed for my bedroom. Underneath the bed will be a workspace, which means that I can get all of my broken tape decks off of the dining room table and into my personal space. I am also designing a shelf to go over the meter bridge of my mixer, which will hold a couple of lamps and my monitors. Finally, I’m designing a normaling RCA patchbay to handle the accessory send/receive jacks on my console. I will be writing a few posts about that later. Let me just say that it’s going to make this thing a LOT less messy:

Messy Patchbay

Anyway. Enjoy the clip. I’ve got some stuff to do.

Hey Jeff,
Sorry it took me a bit. Luckily, the problem was just the fuse connected to the transport section of the machine. Replacing that also fixed the weird timer problems i was having.

That’s all there was to it. I could have used a multimeter to check for continuity on the fuses, saving everyone some time and money. Learning curve? Right here.

I’ll post more pictures of this thing when I get a chance.

Dylan's TASCAM 388

Some time ago, I started an email correspondence with a fellow named Dylan. Dylan had acquired a TASCAM 388 – aka Studio 8 – and he had a few questions about mixdown decks and about TASCAM analog recording equipment in general. A few months later, he emailed back and said that his 388 had stopped working, and he asked if I knew any technicians in the area. I offered to take a look at it myself, in hopes that it would be a simple fix, so that he wouldn’t have to spend money on having a professional look at it. And, I just wanted to see it, because I’d read a lot about these machines and wanted a close-up look at one.

Before I go into specifics on this particular machine’s problem, I want to explain a little about what the 388 is. The TASCAM 388 is an incredible little machine. I say “little” but it’s actually pretty big – 33″x25″x9″ (WxDxH) and I don’t know how many pounds it weighs, but it takes two people to lift it. It records eight tracks on 7″ reels of 1/4″ tape, the transport runs at 7.5ips, and it has a full 8x8x2 mixer section. Also included are built-in dbx noise reduction, search and cue functions, and the option of SMPTE capability through an accessory port on the back.

The 388 is basically a self-contained eight track studio, and it is more than enough for anyone who wants to get into making quality analog audio recordings at home. TASCAM got really good at designing compact headstacks after its initial successes with the Portatstudio line and took things a step further by introducing a product which fell somewhere between a tool for recording demos and a professional recording solution for serious production work.

A good number of 388 users and enthusiasts are out there:

• Foxboro Hot Tubs, a side project by members of Green Day, released an album in 2008, recorded on a 388
• San Francisco artist Kelley Stoltz tracks exclusively on a 388
• The Black Keys recorded their 2003 album, Thickfreakness, on a 388
• And, there are quite a few dedicated 388 enthusiasts on the Home Recording bulletin board.

Anyway, back to Dylan’s 388. It apparently had been working fine for some time. Before it stopped working completely, the tape counter seemed to be losing its accuracy, but it wasn’t too much of a concern to look into. Then – nothing. The machine would turn on, but when a tape was loaded the machine would not play, fast forward, or rewind. The transport engages for a fraction of a second before disengaging completely. Here’s a quick video to demonstrate the issue:

It was pretty puzzling. The tape tension was fine, and the tension arms were engaged. It didn’t appear to be related to the capstan belt, because the tape would move about an inch when I pressed play. It seemed like whatever the problem was, it was something that couldn’t be discovered unless I took the cover off. I was kind of eager to pop the thing open, so I went ahead…

388 Transport

More fun awaits. I will follow up with another post describing what I found, along with a handful of pictures of the 388′s insides.