These good value for money home studio power amps must be one of the most popular home studio amps there is. I guess it is because they look good in a home setting compared with traditional rack mounted gear. Also no fan is a blessing.
Annoyingly the Samson Servo range does suffer from a common intermittent cutting out problem. It manifests itself as the audio cutting out or just fading to a crackle on either channel occasionally, although the sound can break through if a loud passage in the music occurs. Sometimes if you turn the volume it bursts through. It’s a bit like the amp is strangling the audio, but if the audio is strong enough it can prevail.
When I first encountered this I thought it was just the spring loaded speaker wire clips not working too well, and it may be in some cases. Then I thought it was just failing volume control pots as the Samson uses graduated pots I thought they might be prone to failure but no it was something else. So upon further study I realised it was the relay that connects the amp to the speaker terminals. Its job is to isolate the speaker from the amp during switch on; to protect your speakers. The relay contacts have just become dirty and that is what causes your audio to cut out. Replacement of the relay is fairly straightforward and can be done within two hours.
So if your Samson is suffering and you would like to get it fixed please get in touch through my contact form.
Applies to Samson Servo 170 and Samson Servo 260 and other models I imagine. The ideal replacement relay is 24V coil, DPDT @ 8A rating. However I have not been able to find that recent times so have used this one from Farnell G2R-2A DC24
If this post helped you out feel free to donate…
New
Apologies Mikey, been up the walls over the summer and haven’t changed the relay yet, but will do soon as both channels are gone now.
Will let you know how it goes.
So pleased to have found this site, til now I thought the speakers were faulty! I need to replace the relay, and can see several likely looking ones at RS Radionics Ireland, but would be grateful if someone could identify the correct one please.
Thanks in advance, George Hart, West Cork
Hi George, I have looked through my purchase history and added a link to a suitable replacement part from Farnell. Last time I looked I found it hard to get an 8A relay so had to compromise with 5A but it works fine. I had a quick look on the Irish RS site and it looks like 351-588 will be a better choice. Can you double check the dimensions and report back if it works for you ?
Thanks for your prompt reply Mikey!
RS is the one I looked at, and dimensions look correct, though I didn’t measure it as had to reassemble for rehearsal this evening. It’s still working well enough for now but not reliable. I’ll disassemble on Thursday to double check.
Apologies Mikey, been up the walls over the summer and haven’t changed the relay yet, but will do soon as both channels are gone now.
Will let you know how it goes.
Finally replaced the relay today, fits and works perfectly, just had to snip off the ‘normally closed’ terminals. Many thanks again for your help. 😁
It’s rare to find something so useful and so easily. Thank you very much for making this post and keeping it there available to all to see.
I was preparing to replace my trusty Samson 170, and at the last minute just before I was about to bin the amp I googled my symptoms and hey presto, this page pops up at the top.
It was reassuring to see so many people have had this issue and that you offered a service as well as the information to do it yourself.
I ordered the part from https://www.switchelectronics.co.uk/24v-high-power-pcb-relay-8a-dpdt and apart from the 2 additional pins which I removed it was spot on. Took about an hour to do and just about 24hours since ordering the part I’m back up and running sounding fantastic again.
Thank you so much.
Any links to where I can obtain these relays in the USA? We have a popular electronics supplier (mouser) but I find over 1200 results when I look for a 24v DC relay. Thanks!
You will definitely find it on mouser. 24v 8A DPDT and make the pins are similar to the one in other link. If it is 6A or 10A it will be OK. The greater the current rating the better.
servo 550 for me.
I’ve removed and cleaned these relays and it works for a while but the problem comes back. After unsoldering and realising how easy the tops come off I’m pretty sure you don’t even need to unsolder as its such a pain in the a’@;e!
Squeezing the long ends at the base pops the lid so I’d try that first
The 2 relays installed in my 550 are HANKUK RELAY HR-CR311DC024V.
You can get a brand new exact replacement here:
https://www.aliexpress.com/item/1978198703.html?spm=a2g0s.9042311.0.0.55b54c4dHVpcgn
Hope this might help someone….
I would like to summarize my conversation with mikey on Mar. 20.
Sometimes, when your protection relays have been “off (open)” for an extended period, oxidation occurs. So, when the relay goes “on (connected)”, there is a microscopic “film” that has built up between them over time.
An easy “test fix” is to play a song that you enjoy hearing loud, and listen to it as loud as possible. The high audio signal level may be enough to clear the oxidation. I’m not sure exactly why. Ask a scientist .
How about a sledge hammer approach? Remove the relay covers and force them “on” with a tie wrap?
That wouldn’t work properly. Just replace the relay and your amp will be fine for another ten years or so.
It was a joke. My story goes like this : My SERVO – 170 sat, unused, for 2 – 3 years. I fired it up and quickly became aware of sound quality issues. I solved it by playing The Beatles version of “Rock and Roll Music” at full blast. Two minutes and 30 seconds later, all my problems were solved.
I did wonder. But I have to be careful not to give any bad ideas that may be reading. If other readers do try that then remember “It has to be Rock n Roll music”
“gotta be”
Terribly stupid question. I am having the same problem with a Samson Servo 300. I am pretty facile with repairs. I’ve opened the amp — but where is the relay located?? Which board?
Thanks
Eric
The relay is located on the main PCB near the speaker terminals towards the rear of the board. It is a rectangular object about 1 x 3 x 2cm (from memory) usually black but can be other colours too. To replace the part requires desoldering and solder skills and you must be very careful as these PCB tracks carry the speaker output signal so any damage to the track will have an impact on the sound if botched in anyway. Always Take care and take to a tech unless you are qualified and experienced with mains powered apparatus; it can ruin your day very quickly. Mike
Much thanks!
Cheers,
Eric
Will the “Low Profile 8A DPDT Relay 24V Coil” from Spiratronics work for a Servo 260?
The info I have says that it is the same part so should be OK. Check the part numbers carefully.
Hi dude, thanks for this, i was just about to bin mine, as it started on 1 side, then both, do you a fitting guide at all.
Thanks
I don’t have a fitting guide but it is easy if you have Tools and skills most importantly de soldering.
I am trying to fix a Samson Servo 170 with exactly the problem you describe. The problem is that I can find an equivalent relay at Digikey or Newark
I am in the US
The relay in the unit now is: HR-CR3A23DC24H
Can you help?
Thanks!
I usually use this part from local supplier: http://spiratronics.com/low-profile-8a-dpdt-relay-24v-coil.html -= perhaps they can ship to us???
I generally find US has better parts than the UK so keep looking – also ebay might be able to help. I would suggest worth submitting a post on DIYAudio / Music Electronics Forum as there are more US based experts on there.
Good luck with the search.