Data for Motorola SS47 and SPS439 transistors please?

This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hello all.

I need some data/specs on some old Motorola transistors: SS47 and SPS439, both are NPN transistors. They were used in a Marantz 240 amp in the 70s. I cannot find any data on them online. Some people posted on possible replacements for those transistors, but I would still like to see their specs if possible.

Can anyone with a Motorola data book help look these up, please? Or could someone at least point me to which data book to buy?

Many thanks!
Last edited:
Unfortunately, those were the exact imprints on the transistors. Below are the pictures I just took of those exact two transistors.

I'm also attaching the schematic where they are used: in the rectifier/relay board of Marantz 240 amp.


  • Motorola_SS47.jpg
    224.5 KB · Views: 177
  • Motorola_SRS439.jpg
    275.6 KB · Views: 162
  • Marantz_240_Rectifier_Relay_Board.jpg
    135.2 KB · Views: 163
I'll give you at least 2:1 odds that these are manufacturer's house numbers, not Motorola numbers.

Where is the freewheel diode (a.k.a. snubber diode, kickback diode, et al) for relay K301? If these two transistors are in fact defective, the absence of a diode across the K301 coil may be part of the reason. It looks like the circuit designer tried to impress somebody (or just be cute) by using the time constants associated with capacitors C301 and C302 to smoosh K301 through its turn-on and turn-off rather than let it switch sharply. Of course, this will tend to increase contact chatter and wear. C301 and C302 are now 40 year old electrolytic capacitors so they are candidates for replacement on general principles, even without the suspicion that they may have contributed to the failure of Q302 and Q303.

The two transistors themselves are used as a rather unexciting Darlington switch for the K301 coil. Looks like Q302 needs to carry about 100 mA max, and withstand around 60V (plus the turnoff transient generated by K301). It's tough to find anything in a TO-5 or TO-39 package anymore. If you can get a genuine 2N3439 or 2N3440 give them a try - they're high-voltage switching transistors and should be able to swallow some of the spike coming off K301. If you can't get them, try an MPSW42 and bend the leads to fit the PWB pattern.

Q303 should also have a high enough voltage rating to make up for the circuit designer's short sightedness - beyond that it can be just about any run-of-the-mill NPN amplifier with an EBC pinout. Try an MPSA42.

Last edited:
No spec given on the relay, but 24V signal relays usually have coil resistance around 1k. The 560R 5W in series is a voltage dropper as the supply is far more than 24V.

This means that Q302 dissipates a few watts peak during switching, but much less in the steady state . Q303 needs a decent current gain, but only about 1mA current.
I would use a something like a BD130 and a MPS42. Also add a 1N4004 in reverse across the coil
Someone who rebuilt a similar rectifier board in a Marantz 32 used an Omron MY2 relay, which seems to be the right candidate.

Alright, let's catalog replacement suggestions (suggestions from other sources/websites noted with a star *):

Q301, Q303 (SPS439):
*BC546B (or 2N5235)

Q302 (SS47):

Someone with a Marantz 32 (similar rectifier/relay board) measured those original transistors. Original Q301, Q303 (SPS439) give approximately BETA = 100. For Q302, BETA = 60. But again, it's possible that Marantz 32 could have slightly different specs for this board than Marantz 240.

Here's how Marantz describes operation of the relay/rectifier board in Marantz 240 amp:

The output of the power amplifier is applied to the wipers of relay K301 on the rectifier relay board. Relay K301 energizes after a minimum delay of 2 seconds after turn on. The length of the delay is a factor of the time constant of R306, R309, and C302. This delay at turn-on is to prevent any transient surges from reaching the output terminals.

Additionally, resistors R302 and R305 sample the audio output signals. Should a constant DC level over +4.5V or a high-amplitude signal below 10Hz be present, Q301 will turn on, shorting the base of Q303 to ground. C302 begins to discharge, and K301 relay de-energizes.

The relay test in the service manual says that if a 5-Hz signal is fed into the amplifier, the relay should disengage when output voltage is 25.5-33.5 volts.

If a constant DC level over -4.5V is present, the voltage drop across R304 bucks the voltage present at the base of Q303, making K301 relay de-energize.

The output from K301 is applied to the speaker terminals.

86.5 Volts AC is applied to CR301--CR304 (rectifier bridge) which develop +58V and -58V for the power amplifier board. CR305 and CR306 develop the positive voltage to energize K301.

Admittedly, I am not an electrical engineer, and I still struggle to make calculations of voltages/currents on boards like these... But maybe someone could explain to me what kind of voltages are present at the bases, collectors, and emitters of Q301, Q302, and Q303 in the two different modes of operation (Relay on, Relay off).
Recently I repair the RELAY board of a Marantz Model 250M. The relay was energized imediately after plugging the power cord, without any delay. I replace the 3 transistors and all the 3 capacitors for new ones :
Q301 and Q303 (originaly SPS439) for BC546B, flipping the face of transistors around cause the pinout is diferente (CBE), the SPS439 is EBC.
Q 302 (originaly SS47) for BD911, bending the leads to fit the board. SS47 is CBE and BD911 is BCE. BD911 has maximum ratings near BD130 like Vcbo =100 volts, enough to work with +58 DC voltage of the relay circuit. The BD911 is mounted in Jedec TO-220 plastic package.
C 301 for 22uF X 25 V
C302 for 220uF X 50V
C 303 for 22uF x 63V
Now the relay energizes after 6 seconds AC power is applied to the unit. Additionaly I replace the 2 main filters of 20.000uF (capacitors C1 and C2) for new ones.
The sound is great !!! After 40 years this amplifier remanis as the state of art of american transistor era.
Guys, Thanks for these informations that were very useful !
Alex Haidar
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.