Diagnostic Audiometer C.A.S.-10  - Page 1
Forum section: electronics / repair

author: vidarr
author_rank: Frequent Contributor
timestamp: October 30, 2018, 12:52:05 am
content: My wife found this audiometer on the curb. This is one of those things where it has so many good parts, but not sure if I should take it apart. I am still working on the other projects, I posted some on here, so this will sit for a while, while I think about it.The power cord is cut off, and it is missing the covers for the two fuses on the back. On the inside, one wire broke lose from a dial. Other than that, it is in very good condition (visually). The inside looks almost brand new and very well organized.What do you guys think? Is this one of those cool, vintage things you do not make other projects out of?Thanks!

author: coromonadalix
author_rank: Super Contributor
timestamp: October 30, 2018, 01:17:41 am
content: Looks like an audio generator ? to test ears frequency response ?

author: vidarr
author_rank: Frequent Contributor
timestamp: October 30, 2018, 12:35:29 pm
content: Yes. Exactly. It has a lot of parts in common with synthesizers though. In this case, vintage synthesizers. I am not into that kind of stuff (anymore -- like 30 years ago), but I think all the hipsters are.A lot of projects could be made with the parts of this thing. But, it would be a shame to wreck such a work of art the insides of this are. The entire thing is hand made. Even the every single wire (almost) is hand-painted/coded. Every connection was done by hand. But, damn, those pieces in there would look cool in some other projects. Hmmm.

author: t1d
author_rank: Super Contributor
timestamp: October 31, 2018, 09:31:50 am
content: Well, maybe you can have your cake and eat it, too. Repair the unit, for the sake of the artwork. Sell it, to buy new, cool parts.Check Ebay, for its value. It might even be worth something as "for parts only."

author: vk6zgo
author_rank: Super Contributor
timestamp: October 31, 2018, 12:08:41 pm
content: I used to calibrate,& sometimes, fix these sort of devices.I vaguely remember that particular model.Although most of the newer stuff was controlled from a laptop, there was still a lot of older standalone gear around.The audiometer headphones must deliver a precise sound pressure to the ear of the person under test.To this end, Audiometers (complete with headphones) are calibrated using an artificial ear, which is in turn calibrated in an Acoustic Standards lab.In the local calibration, each of the headphone earpieces are placed on the artificial ear, & a series of tests are carried out, including absolute output capability, frequency response, noise & distortion.A calibration chart is drawn up for both channels.They are rather nice pieces of equipment, but whether they are worth keeping for historical interest isanyone's guess.It might be worth contacting the manufacturer to see if they have a Museum,which may need an example of that model.Otherwise, I'd probably pull it apart for the useful bits.

author: Xwell
author_rank: Newbie
timestamp: January 23, 2019, 06:08:08 pm
content: Good Morning,I guess I'm directing my question at vk6zgo as you have stated that you used to repair these kind of units.I was searching around looking for info on an audiometer that I picked up in a local municipal auction. It's an AMBCO 650AB model. It's a complete unit with testing headphones, patient response button, and a power supply. It works great on all but one frequency. I pulled the frequency selector switch and verified that it is working correctly. I don't have much component-level testing experience, but I'm comfortable with a soldering iron and wouldn't shy away from replacing a few resistors if it will get this thing working again. I see a few resistors that appear to be discolored. Should I just pull them and test them individually? Do you have any suggestions on what else could be the issue? Thanks for any info you can pass along. I've attached a couple of photos of the board. The darkened resistors can be seen in photo 4. Specifically R8, R15, R16, and R23.Thanks again

author: GLouie
author_rank: Regular Contributor
timestamp: January 23, 2019, 07:01:06 pm
content: Xwell, I don't know your device, but there is nearly zero chance those resistors are bad - they just came from the factory in a different color. They don't change color without leaving heat marks on the board.With no schematic or signal tracing info, I'd look at those black Piher adjustable resistors. They likely either control the frequency or level of each test frequency. Jiggle the one for the frequency that doesn't work.Otherwise, you can look for bad solder joints, then you need to do some signal tracing and see what happens with working frequencies vs. your non-working frequency.