Bench power and a '79 wow and flutter meter

S

Scripps-66

New member
Hi guys, from a lack of any place to have a tape machine worked on here in the Memphis area, I've been learning through trial and error
to work on machines myself, I'd like to have the ability to test circuits on pcb boards in my tascam machines without relying on machine power, do any of you use bench power? I've looked at some of the cheaper models and from what I can tell they have DC only, unless I'm just totally reading the specs wrong, I dont think I'll need bench power for anything beyond PCB boards for these 1/2 inch tape decks and if any of you out there have a unit youd like to recommend? And will I need A/C power? Or perhaps do these 'DC only' units actually do have A/C and I'm just an idiot? (totally a possibility) one more question about wow and flutter meters, I'm looking at a vintage meter from 79 that looks very clean and unused, do these old units wear out of calibration from sitting? It's in its original box with original manual for what it's worth, any replies are greatly appreciated
 
What meter (make and model)?

I use bench supplies all the time. Almost all the power in your Tascam machines is regulated DC power. The only AC rail I occasionally come across is for meter lamps, but more often than not it’s DC. The trick is getting a bench supply with the oomph for driving a transport if you are truly wanting to keep the machine off the mains power, but how often do you actually need to do that? Like, I use the bench supply when I have a board out of the machine on the...wait for it...bench. If I’m having to test the transport it’s plugged into mains power. If something isn’t working right I’m sleuthing to narrow down what board may be housing the cause of the problem and then depending on the circumstances am pulling that out and passively testing (tracing out circuits using continuity), or in most cases am testing in-circuit using an oscilloscope. Sometimes the bench supplies are necessary, other times not. It just totally depends. But I do like having them. You want something with variable voltage, ideally a dual supply (since most of what you are working on if you are working with the audio circuits is powered by a dual supply), being able to power down to 5V on up to 24V is nice, current limiting is nice to avoid cooking stuff, and 1A capability is nice, but at least 500mA. But I went for a long time without having a bench supply. I think first it’s a multimeter that is rated for audio bandwidth, then a scope, then bench supplies. Others may disagree. In fact i hope others chime in. Would be nice to get others’ perspectives.
 
Hey sweetbeats sorry for the delay.. the w & f is a BPI 1600, the only thing I'd use the bench power on is testing out pcb's.. found a digital power supply on Ebay for $40, its leader 718 3d.. saw a guy on YouTube who hooked up a pcb to bench power and he had these small slide on connectors that were small enough for the pins on the pcb plug ins instead of alligator clips, looking to get those... just bought a oscilloscope, I've never owned one have no idea how to use, still waiting on probes to come in (my scope didn't come with any) down the road when I get a feel for this oscilloscope I'd like to use that for tracking down bad circuits.. any advice on shortening a learning curve on using a scope? It's a Hewlett Packard 54600A 2 channel scope if that helps
 
If you need better access to the circuit board for testing then the standard way to do it in a professional machine is to use an extender card to bring the card you want to test out in front of the other cards. Another way to do this is to make extender cables so that you can run the board out of the machine but still connected to it.

The best way to use an oscilloscope on most audio electronics is to work out the signal flow from the circuit diagram, inject a tone into the input and then use the oscilloscope to see how far that tone goes before it stops. When you've found where it stops you've found the fault.
 
Thanks James, I'll try the scope.. curious about the extender cards, would that involve finding matching plugins for the tsr8 PCB's? Are they fairly easy to find?
 
If you were going to do it yourself you would need to find matching connectors of both genders and either connect them with ribbon cable or make a circuit board the same size as the original with the matching connectors on each side so that the channel card would sit in front of the others to allow you to work on it. I must admit that I don't know how easy it is to find the connectors that you would need to make up an extender card.

Another method you can use in the absence of an extender card is to remove the other channel cards to give you access to the card you want to work on.
 
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