Hello, I repaired by XPS2 as it no longer had enough output to power the turntable motor. As per earlier thread the XPS2 service manual is here:
https://www.vinylengine.com/library/roksan/xps2.shtml
Firstly here are some notes on the circuit diagram as it is a bit sparse. IC 706 is an M706 counter, pin 8 is Vcc (+15V) and pin 5 is GND (0V). IC 324 is an LM324 op-amp, pin 4 is +Vcc (+15V), in 11 is GND (-15V). OP1 and 2 are LM1875T power amp ICs,pin 5 is V+ (+28V) and pin 3 is V- (-28V).
I added some further labels to the circuit diagram as follows. Outputs A (shown as AA by mistake) and C are 90 degree phase, one of these is connected to E and hence OP1. Outputs B and D are 0 degree phase, one of these is connected to F and hence OP2.
The capacitor and resistor on the - input to OP1 are C26 and R7, and that on the - input to OP2 are C25 and R5.
A few years ago I replaced most of the mini electrolytic caps, these are annoyingly small and fail due to overheating. This year a few of them needed replacing again, PSU was still not working. I found that the 33/45 and the Operate/Standby switches were high resistance, Fortunately pressing them many times restored the contacts.
I found that C25 and C26 had both failed being close to the hot LM1875 chips. When replacing them I lifted the opposite end of the corresponding resistors (R5 and R7) and soldered the new caps between the resistor lead and ground, then shorted the old C25 and C26. This left the new caps further away from the hot ICs. I now had outputs from both OP1 and OP2, but the OP1 (90 degree phase) AC output voltage was half that of OP2 (0 degree phase). It was only when I connected a scope that I saw that OP1 output was not a continuous sine wave but rather a series of bursts of sine followed by no signal. Replacing the LM1875T for OP1 restored normal output and the turntable was back in use.
Also note that the 22k ohm resistors between OP1 / OP2 output and - input are SMD parts on the track side of the PCB. I lost one so replaced with a resistor with leads.
Regards,
John
https://www.vinylengine.com/library/roksan/xps2.shtml
Firstly here are some notes on the circuit diagram as it is a bit sparse. IC 706 is an M706 counter, pin 8 is Vcc (+15V) and pin 5 is GND (0V). IC 324 is an LM324 op-amp, pin 4 is +Vcc (+15V), in 11 is GND (-15V). OP1 and 2 are LM1875T power amp ICs,pin 5 is V+ (+28V) and pin 3 is V- (-28V).
I added some further labels to the circuit diagram as follows. Outputs A (shown as AA by mistake) and C are 90 degree phase, one of these is connected to E and hence OP1. Outputs B and D are 0 degree phase, one of these is connected to F and hence OP2.
The capacitor and resistor on the - input to OP1 are C26 and R7, and that on the - input to OP2 are C25 and R5.
A few years ago I replaced most of the mini electrolytic caps, these are annoyingly small and fail due to overheating. This year a few of them needed replacing again, PSU was still not working. I found that the 33/45 and the Operate/Standby switches were high resistance, Fortunately pressing them many times restored the contacts.
I found that C25 and C26 had both failed being close to the hot LM1875 chips. When replacing them I lifted the opposite end of the corresponding resistors (R5 and R7) and soldered the new caps between the resistor lead and ground, then shorted the old C25 and C26. This left the new caps further away from the hot ICs. I now had outputs from both OP1 and OP2, but the OP1 (90 degree phase) AC output voltage was half that of OP2 (0 degree phase). It was only when I connected a scope that I saw that OP1 output was not a continuous sine wave but rather a series of bursts of sine followed by no signal. Replacing the LM1875T for OP1 restored normal output and the turntable was back in use.
Also note that the 22k ohm resistors between OP1 / OP2 output and - input are SMD parts on the track side of the PCB. I lost one so replaced with a resistor with leads.
Regards,
John
Hello again,
My XPS2 died again, turned out it the LM1875T on OP1 had failed (same IC I replaced 3 years ago). I popped a new one in, and tried to improve the heatsinking by sanding off the paint between it and the case, adding some heatsink paste. I had used thin rubber TO220 insulators (can't use paste) between the 4 ICs and the heatsink, I've read that these are not as effective as mica insulators (with paste). Also I will now power the XPS2 off when not using the turntable, before it was left on 24/7.
Next time I will consider using an external LM1875T based stereo amplifier for OP1/OP2.
Regards,
John
PS I see Roksan has stopped making turntables, are there any suggestions on who in the UK does Roksan Xerxes repairs please?
My XPS2 died again, turned out it the LM1875T on OP1 had failed (same IC I replaced 3 years ago). I popped a new one in, and tried to improve the heatsinking by sanding off the paint between it and the case, adding some heatsink paste. I had used thin rubber TO220 insulators (can't use paste) between the 4 ICs and the heatsink, I've read that these are not as effective as mica insulators (with paste). Also I will now power the XPS2 off when not using the turntable, before it was left on 24/7.
Next time I will consider using an external LM1875T based stereo amplifier for OP1/OP2.
Regards,
John
PS I see Roksan has stopped making turntables, are there any suggestions on who in the UK does Roksan Xerxes repairs please?
You should not leave these powered on 24/7. Serves no purpose and these generate too much heat for an enclosed casing.
XPS2 is a single box. These were a poor design so I expect most will have failed by now.
I left all my HiFi on 24/7 (well for many days at a time at least) as things like the power amp sounded better once warmed up. Leant the hard way this is not a good idea for the XPS2!
Regards,
John
I left all my HiFi on 24/7 (well for many days at a time at least) as things like the power amp sounded better once warmed up. Leant the hard way this is not a good idea for the XPS2!
Regards,
John
All I can say is that I upgraded my XPS to a 2 box unit as part of a full service with Roksan 25 years ago and that has worked without fail since. I never liked how warm the original got, although the matching veneer was a nice touch. I have found one repair source in UK but the website concerns me a little. A google for 'PR audio' will find them.
Please consider way larger heatsinks and ventilation slots as these are errors by design (with a user error combined).
There should be large(r)/extra air inlets close to the heatsinks and also ventilation slots at the upper cover above the heatsinks (a large milled slot is most appealing). The existing inlets can be enlarged easily. Metal work is nice and relaxing and in this case quite rewarding. Just work slow and precise, deburr holes and possibly repaint the chassis or use a little paint at the holes to avoid corrosion. I think having one is quite unique as most have perished from heat. AFAIK later ones were slightly improved.
There should be large(r)/extra air inlets close to the heatsinks and also ventilation slots at the upper cover above the heatsinks (a large milled slot is most appealing). The existing inlets can be enlarged easily. Metal work is nice and relaxing and in this case quite rewarding. Just work slow and precise, deburr holes and possibly repaint the chassis or use a little paint at the holes to avoid corrosion. I think having one is quite unique as most have perished from heat. AFAIK later ones were slightly improved.
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Thanks for the replies / suggestions. As I wrote earlier, Roksan has stopped making / selling turntables and hence also power supplies. Are there any good Xerxes support experts in the UK? Or any recommendations for 3rd party power supplies? The Xerxes needs 16V AC 2-phase supply, like a lot of other AC motor decks.
Regards,
John
PS I have looked today at 2nd hand Sondeks on ebay (yes I know, the dark side!), prices seem really high, especially for original 1979 models - I guess like a lot of classics prices were a lot lower 20 years ago.
Regards,
John
PS I have looked today at 2nd hand Sondeks on ebay (yes I know, the dark side!), prices seem really high, especially for original 1979 models - I guess like a lot of classics prices were a lot lower 20 years ago.