THE THREE MAIN COMPONENTS TO A
THE FIVE MOST COMMON
1. Unit does not turn on
2. Display shows but no sound
3. Audio is not as good as it should be
4. Loud crackly sounds come and go
5. Unit is turning off by itself
UNIT DOES NOT TURN ON
Check to ensure that your battery is giving full voltage. Dopplers are sensitive to voltage
drops and will automatically shut down or not turn on at all, if less than the specified volts.
Even new batteries can come off the shelf with less than specified voltage. Stick with name
brand batteries such as Energizer.
If there is any reaction on the numeric display to simulation on the probe, your speaker is
faulty and you should review the following slide
Does the power button work intermittently? If yes, you may need to replace the switch on
your doppler. These are available for select models to be replaced at the board level repair.
If you choose to open your doppler, look for water damage on the board. This is very
common and most dopplers have reasonably priced replacement PCB’s. It is usually not
worth your time to trace a PCB that has water damage, as it will often have damaged the
main chip or other components in the process.
Make sure that there is no debris under the main power switch that would interfere with the
motion of the mechanical movement. If it is a membrane switch, try crossing the terminals at
board level. Our technician will be happy to assist you in identifying the correct terminals. If
crossing them works, then replace the switch component for that doppler.
DISPLAY SHOWS BUT NO SOUND
The first step is to rule out the speaker by connecting a set of headphones into the jack on the
doppler. If you receive proper sound this way, your speaker needs replacement or reconnection.
Once the speaker is ruled out, you should try to simulate a heart beat on the probe to see if
the display changes to show the activity from the probe. If there is no display, you can easily
change the cable on most dopplers. Some use standard telephone cables and you can exchange it for
a known operational cable from any phone. You can also check the continuity of any cable to ensure
there is no breakage.
Once the cable is ruled out we are left with the probe and the most common issue with probes is
broken crystals. Some manufacturers offer replacement crystals and others offer replacement
probes. All are available through Stat Medical.
In a rare occasion, the PCB in the probe is damaged. This is rare however, they are available
through Stat Medical for some makes of dopplers.
In the event of a waterproof obstetrical probe, these are generally not repairable and are
available on service exchanges through Stat Medical.
If both the Crystal and the casing are obviously damaged, it is better to replace the whole unit
and Stat Medical carries a large inventory of replacement probes for most makes of dopplers.
AUDIO IS NOT AS GOOD AS IT SHOULD BE
This problem carries a lot of the same solutions as a doppler with no sound although it is more easily
identifiable where the problem is.
First rule out the speaker as mention in the previous slide
A cable will not create this issue.
Check that the Battery is running full voltage under load.
Once the speaker is ruled out, it leaves the main suspect to be the probe.
The ultrasound crystals are place on the inside of the probe tip and by pressing on the probe tip
with moderate pressure, you can determine if there is a crack in the crystal. You will hear squelch
or static by pressing on the tip if there is a crack in it. You will not be able to see the crack but it
will sacrifice the sound.
Replacement Crystals are available through Stat Medical for some makes of doppler probes while
replacement probes are available for the others.
In the event that there is no sound difference when pressing on the crystal tip and the speaker is
proven to be good, the last thing to check is the tuning of the crystal. This is the gain pot on the
probe PCB and generally requires proper equipment to tune it appropriately. It should be sent in
NOTE: If you have purchased a lower cost doppler, it will not produce the sound equivalent to the
better quality models. Make sure that you are comparing sound quality with comparable models.
LOUD CRACKLY SOUNDS COME AND GO
Firstly ensure that the user is using sufficient transmission gel to cover the whole tip of the
Ensure that there are no high powered electrical devices in the near vicinity. Even power lines
and fluorescent lights are known to cause interference with dopplers.
Try wiggling the cable while it is turned on to see if there is a short in the wiring that is causing
the sounds to come and go. On models that use standard phone cable, try replacing it with a good
cable. The cords are often stretched and bent while in use. Replacement cords are available
through Stat Medical.
Once you have ruled out the cable, move to the probe and use the same pressure techniques on
the probe tip explained in the previous slide to see if you can reproduce the sound. You may have
a slight fracture on the crystal tip.
If you are going to open the main unit, inspect the speaker for water damage or dried out paper.
Usually the speaker will be continuously crackly rather than intermittent. Speakers are available
through Stat Medical
UNIT IS TURNING OFF BY ITSELF
This is almost always a voltage issue that is caused by depleted batteries or insufficient volts
Try replacing the Battery with one that has appropriate voltage under load. Be sure to use
a good quality battery.
If this doesn’t fix the problem, you should open the main unit and look for water damage on the
If this is a rechargeable unit, ensure that you AC adaptor is producing the accurate output voltage
as required on that specific model.
We do not recommend the use of non-OEM rechargeable batteries with dopplers as this has
been the cause of many problems.
The Typical Components Available
Through Stat Medical
Probe PC Board
All external casing and
labeling is available
HOW CAN STAT MEDICAL HELP
Free Telephone tech support for Dopplers purchased from Stat Medical.
Free Parts Listing.
Warranty Coverage for some makes of dopplers. *
A Large inventory of repair parts for many makes of dopplers.
Repair service available.