|
Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
|
Thread Tools |
16th Nov 2014, 10:13 am | #1 |
Pentode
Join Date: Jul 2005
Location: London, UK.
Posts: 193
|
Fault with Solartron SRS151
Hello,
I have a Solartron SRS151 which i've used for many years successfully. It has 6 KT66 It went 'Thunk' the other day after few seconds and the 5A fuse went off in the plug as well as having damaged the mains switch in the power supply! I originally thought it could have been the mains switch but the problem seems to be caused by something else. I've therefore used a variac to power it gently to try understand where the fault is coming from. A wattmeter shows 100W ish half way through when using the variac. If i continue to increase the voltage, i can see that a third extra relay (retrofitted in the SRS151 as a HT surge protection) is coming on (although RL2 A&B are not even switched-on!!) and the 3A fuse in the plug gets killed straight away at the same time. I put a 3A fuse to avoid significant damage which should be ok when the power supply is idle. I've attached the schematic with the diagram of the third relay. There is a resistor in parallel on the 3rd relay for detecting the HT current. In my case, RL2 A&B are not switched on so it is therefore a little strange that this relay is activating as there is not meant to be any HT current going through. I tried to search for insulation type problem using a ohmmeter between the various separate windings as well as checking if the mains primary is connected to the screen but cannot find any isolation issues. I also checked the 2 native relays (RL1 and RL2) which may be suspicious as their coil are connected to the mains and could be leaking to the earth via the chassis. It's unclear what makes the fuse blow up and whether the excessive mains current is between the neutral and live or live and earth. I was wondering whether i can use a 100W lamp as ballast to power the beast to avoid killing a fuse every time ? Do you recommend other things to check and a particular methodology for detecting the fault? The transformer seems to have been built to last though. Thanks Thierry.
__________________
BVWS Member. |
16th Nov 2014, 3:05 pm | #2 |
Octode
Join Date: Jan 2009
Location: Falmouth, Cornwall, UK.
Posts: 1,987
|
Re: Fault with Solartron SRS151
What are the rectifiers, difficult to see on the schematic. Any chance of something larger please.
__________________
Stephen _________"It`s only an old telly" ___ |
16th Nov 2014, 4:15 pm | #3 |
Pentode
Join Date: Jul 2005
Location: London, UK.
Posts: 193
|
Re: Fault with Solartron SRS151
Rectifiers are 3 x FW4-800 in parallel for the HT voltage.
I attach a PDF about the circuit diagram (without 3rd relay) Circuit diagram/manual from this thread https://www.vintage-radio.net/forum/...n+power+supply Thanks Thierry.
__________________
BVWS Member. Last edited by delaitt; 16th Nov 2014 at 4:32 pm. Reason: 3 x FW4-800 |
16th Nov 2014, 4:26 pm | #4 |
Pentode
Join Date: Jul 2005
Location: London, UK.
Posts: 193
|
Re: Fault with Solartron SRS151
Looks like Peter G3PIJ had a similar fault with its SRS151, although cause is not known (see at the end of the thread):
https://www.vintage-radio.net/forum/...ad.php?t=26663 The smaller relay described by Peter G3PIJ is RL1 (for switching between secondary 420 and 620 V HT voltages). Thierry
__________________
BVWS Member. |
16th Nov 2014, 4:33 pm | #5 |
Pentode
Join Date: Jul 2005
Location: London, UK.
Posts: 193
|
Re: Fault with Solartron SRS151
Could it be that there is a short one of the FW4-800?
Thierry
__________________
BVWS Member. |
16th Nov 2014, 7:30 pm | #6 |
Octode
Join Date: Jan 2009
Location: Falmouth, Cornwall, UK.
Posts: 1,987
|
Re: Fault with Solartron SRS151
Sorry, been out all day. I was thinking the same thing with a possible rectifier fault.
__________________
Stephen _________"It`s only an old telly" ___ |
16th Nov 2014, 8:38 pm | #7 |
Nonode
Join Date: Jun 2007
Location: Coulsdon, London, UK.
Posts: 2,152
|
Re: Fault with Solartron SRS151
If you remove all the valves and start it using a 100W lamp limiter you could eliminate transformer faults.
Have you checked the reservoir capacitors? |
16th Nov 2014, 8:54 pm | #8 |
Nonode
Join Date: Jun 2007
Location: Coulsdon, London, UK.
Posts: 2,152
|
Re: Fault with Solartron SRS151
If contacts RL2/A are open it could narrow the fault down to the components in the power supply i.e. rectifiers and sockets, capacitors, inductor and fuse.
A leakage to earth in one of these would draw a heavy current and operate relay 3. If you soldered a 1N4007 diode to a 200K resistor and used it in one of the rectifier sockets as a current limited rectifier you could see if the capacitors charged up. |
16th Nov 2014, 11:18 pm | #9 |
Pentode
Join Date: Jul 2005
Location: London, UK.
Posts: 193
|
Re: Fault with Solartron SRS151
it looks like the secondary windings for the two HT, FW4-800 (2x420 or 2x620) and AZ31 (2x400) are shorted via 500 ohm. In addition, these two HT windings have a 1.5Mohm insulation resistance with the mains primary winding
The other windings are ok except these. It's probably the end for this power supply unless i can find a spare transformer... Thierry.
__________________
BVWS Member. |
17th Nov 2014, 9:26 pm | #10 |
Dekatron
Join Date: Feb 2005
Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW
Posts: 3,517
|
Re: Fault with Solartron SRS151
Might be able to help you there......
__________________
Engineers make things work and have spare bits when finished |
17th Nov 2014, 11:09 pm | #11 |
Pentode
Join Date: Jul 2005
Location: London, UK.
Posts: 193
|
Re: Fault with Solartron SRS151
Thanks Sean
__________________
BVWS Member. |