G’day
The Mains voltage here in Northern Sydney averages 250V, the upper end of the supposed 230V nominal range.
I have a 220V rated Yaqin MC5881A it’s always given off some heat but sounds great so no worries, she’ll be right.
Recently I had to replace the volume pot and whilst tracing the fault and conferring with various threads here realised the internal voltages are out if spec.
Secondary 376VAC
B+ 474V
Heater is 7.56VAC
There are a number of recommended internal adjusts on this site. However I realise that I probably need a new power transformer.
1) any other suggestions?
2) how do I best find a suitable spec transformer ?
3 anything else to consider?
Phillip
The Mains voltage here in Northern Sydney averages 250V, the upper end of the supposed 230V nominal range.
I have a 220V rated Yaqin MC5881A it’s always given off some heat but sounds great so no worries, she’ll be right.
Recently I had to replace the volume pot and whilst tracing the fault and conferring with various threads here realised the internal voltages are out if spec.
Secondary 376VAC
B+ 474V
Heater is 7.56VAC
There are a number of recommended internal adjusts on this site. However I realise that I probably need a new power transformer.
1) any other suggestions?
2) how do I best find a suitable spec transformer ?
3 anything else to consider?
Phillip
USA has exactly the same problem for folks with antique power transformers, and the really beautiful mil-surp transformers are all antiques now. Temporary solution is to commandeer a Variac, but the long term solution is to make a "bucking transformer" box. Power input comes from the wall, and inside is a big filament transformer wired like an autoformer, with primary and secondary in series, and output taken across the primary.
So, for folks living their summer now (how does *that* work?), an old filament transformer of 230VAC primary and 20 - 25 VAC or so of secondaries, in series from the wall, output from across the 230VAC. Put it in a nice safe box with pretty wires and you're golden.
YOS,
Chris
So, for folks living their summer now (how does *that* work?), an old filament transformer of 230VAC primary and 20 - 25 VAC or so of secondaries, in series from the wall, output from across the 230VAC. Put it in a nice safe box with pretty wires and you're golden.
YOS,
Chris
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You could try a mains stabilizer, saturation transformer.
Nowadays i build amplifiers completely regulated with regulated heaters, and high voltage.
Nowadays i build amplifiers completely regulated with regulated heaters, and high voltage.
Yes +6% of 230V is the utility obligation. I often reach 248V during the day (due to nearby PV on my phase), and 241V nominal otherwise. Swings and roundabouts, as they have a -10% of 230V obligation, but loading is getting less severe as equipment becomes more efficient.
All I can recommend is to make the bucking transformer safe (eg. include a combo IEC/fuse, and fuse for the secondary current rating, especially if using say a 240/24V 2A style PT), and wire the primary across the lower output voltage, not the input higher voltage.
Oh and send your distributor a kind note to say what you have measured and that it would help if they reduced the tap setting for your local LV distribution, even if they won't. Not many/any of the smart meters seem to tell the distributor the local voltage, so unless they have reports coming in then they won't know.
Moderator edit: Please see post #13 for erratum
All I can recommend is to make the bucking transformer safe (eg. include a combo IEC/fuse, and fuse for the secondary current rating, especially if using say a 240/24V 2A style PT), and wire the primary across the lower output voltage, not the input higher voltage.
Oh and send your distributor a kind note to say what you have measured and that it would help if they reduced the tap setting for your local LV distribution, even if they won't. Not many/any of the smart meters seem to tell the distributor the local voltage, so unless they have reports coming in then they won't know.
Moderator edit: Please see post #13 for erratum
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If you can get a motorized one surplus, its not that hard to make a little controller that does that automatically as well.
Bucking transformer is by far the best solution. Easily done, check the list of dual primary, dual secondary transformers for 50/60 Hz by Hammond. A one time fix, far cheaper than a Variac for a rather permanent application.
Hammond Mfg. - Power Transformer - Dual Primary / Dual Secondary (266 Series)
Hammond Mfg. - Power Transformer - Dual Primary / Dual Secondary (266 Series)
Report it to your electric company. First, be sure your reading is correct. Read the voltage with 2 or more different meters and be sure they correlate, or have your meter calibrated using a known AC source. If you have lamp and appliance failures, that's a good sign that the voltage is too high, too. It's an electric company problem if the voltage is in fact that high.
@ egellings, 250V is not unusual here.
If I were in this situation I'd be inclined to make the adjustment. As it is I do use vintage power transformers and I like to see more than 6.3V, as it can be padded down.
If I were in this situation I'd be inclined to make the adjustment. As it is I do use vintage power transformers and I like to see more than 6.3V, as it can be padded down.
Totally agree - there are a huge number of 12V 50W transformers being ripped out by sparkies and thrown away. Some of those transformers had dual primary windings (ie. 115+115) so could at least be used as output transformers, but most don't.
The problem lies in the Electric company.
As You know power comes from a transformer nearby and then travels along the road cables to Your house.
People living next to the transformer get higher Voltage than those living on the far end of the line. There is a length limit for those cables and perhaps Your Voltage is high because the cable is too long and needs this length in order to provide Voltage to the last house on the road, and they have cut costs not installing another transformer or installing a new cable from another transformer for those last houses.
You could move to another house further away or talk to the company as they can adjust the Voltage at the transformer.
Ask them to install a metering log device for a few days in order to find out if Voltages are out of spec and then start claiming with the help of Your neighbors.
I have a friend who runs a wedding venue and one time he asked me for help, since his PA gear was shutting down. I've measured the Voltage and one phase was running at 160-170V. Nominal is 230/400V. He started to use a Diesel generator on most of the events.
He claimed & claimed and last year they installed another cable coming from the other side of the street and now the DJ's are happy.
As You know power comes from a transformer nearby and then travels along the road cables to Your house.
People living next to the transformer get higher Voltage than those living on the far end of the line. There is a length limit for those cables and perhaps Your Voltage is high because the cable is too long and needs this length in order to provide Voltage to the last house on the road, and they have cut costs not installing another transformer or installing a new cable from another transformer for those last houses.
You could move to another house further away or talk to the company as they can adjust the Voltage at the transformer.
Ask them to install a metering log device for a few days in order to find out if Voltages are out of spec and then start claiming with the help of Your neighbors.
I have a friend who runs a wedding venue and one time he asked me for help, since his PA gear was shutting down. I've measured the Voltage and one phase was running at 160-170V. Nominal is 230/400V. He started to use a Diesel generator on most of the events.
He claimed & claimed and last year they installed another cable coming from the other side of the street and now the DJ's are happy.
OOPS, my tolerances were wrong in post #4. It should have been +10% and -6% of 230V nominal - doh!
MAACO, it is a very rare situation in Australia that domestic voltage goes outside the allowed +10% and -6% limits. Within that tolerance the distributor (electric company) does not have to tweak the tapping at the nearest serving HV to LV transformer.
That means the OP would have to measure at least 253V for the 'electric company' to have an obligation to make a change. They may well check on that phase for the amount of installed PV, and identify a scenario of loading and generation where 253V could be exceeded at end of line, and hence schedule a tap change. That change could even be instigated by new PV installation permissions (as Australia has a substantial level of domestic PV and that level is till increasing due to available subsidies and lowered cost of PV and inverters), as I know in the past that some PV permissions for commercial premises have been rejected due to unacceptable end-of-line voltage tolerance levels.
The situation can also be exacerbated if the home has PV installed itself, as the mains voltage tolerance only applies up to the PCC (house boundary). Also new PV installations are not getting smaller, as most commercial installers offer a package based on 'cost', and the falling price of PV panels and inverters means there is more 'PV power' in each new install. Maybe (or hopefully) the voltage trend will swing back as more and more houses become early adopters for batteries, as battery related subsidies are just starting.
MAACO, it is a very rare situation in Australia that domestic voltage goes outside the allowed +10% and -6% limits. Within that tolerance the distributor (electric company) does not have to tweak the tapping at the nearest serving HV to LV transformer.
That means the OP would have to measure at least 253V for the 'electric company' to have an obligation to make a change. They may well check on that phase for the amount of installed PV, and identify a scenario of loading and generation where 253V could be exceeded at end of line, and hence schedule a tap change. That change could even be instigated by new PV installation permissions (as Australia has a substantial level of domestic PV and that level is till increasing due to available subsidies and lowered cost of PV and inverters), as I know in the past that some PV permissions for commercial premises have been rejected due to unacceptable end-of-line voltage tolerance levels.
The situation can also be exacerbated if the home has PV installed itself, as the mains voltage tolerance only applies up to the PCC (house boundary). Also new PV installations are not getting smaller, as most commercial installers offer a package based on 'cost', and the falling price of PV panels and inverters means there is more 'PV power' in each new install. Maybe (or hopefully) the voltage trend will swing back as more and more houses become early adopters for batteries, as battery related subsidies are just starting.
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I have not suffered from appliance failures (although this was the frustrating case at a previous home 😡 )
Voltage checked with Fluke 117 Electricians MultiMeter, Smart Utility Meter and PV system (yes, solar may add to the problem but doubt its the cause)...
Unfortunately, I am not hopeful of the electricity supply dropping voltages by the supplier. It's a commonly reported issue but I will follow up regardless.
Thanks
Attachments
Power supply transformer transplant
When I just checked my utility meter is reading 253V. I have PV but that in itself is not the root cause as I could turn off my inverter and still get 250V. It's a more general issue. However I will contact the electric company and see where that goes.
In terms of solution, I am looking for permanent and elegant fix leaning towards sourcing a replacement transformer which I am capable of safely and competently transplanting.
I am wide open to suggestions but I want to avoid cumbersome external supplies if possible. I'm not against adding regulation although it detracts from the thermionic character of the amp but foresee non-trivial power dissipation and noise considerations. I presently don't have access to a non-aesthetically challenged Variac 😉
Apart from physical dimensions, primary voltage (230-250V), secondary voltages (~310V,6.3V) what are the key parameters?
I haven't calculated power requirements TBD but the audio output power is 2x46W
Any supplier recommendations servicing Sydney? I am aware of Hammond, and can trawl the usual Aliexpress and Ebay.
Any shared experiences welcome including pitfalls to avoid?
When I just checked my utility meter is reading 253V. I have PV but that in itself is not the root cause as I could turn off my inverter and still get 250V. It's a more general issue. However I will contact the electric company and see where that goes.
In terms of solution, I am looking for permanent and elegant fix leaning towards sourcing a replacement transformer which I am capable of safely and competently transplanting.
I am wide open to suggestions but I want to avoid cumbersome external supplies if possible. I'm not against adding regulation although it detracts from the thermionic character of the amp but foresee non-trivial power dissipation and noise considerations. I presently don't have access to a non-aesthetically challenged Variac 😉
Apart from physical dimensions, primary voltage (230-250V), secondary voltages (~310V,6.3V) what are the key parameters?
I haven't calculated power requirements TBD but the audio output power is 2x46W
Any supplier recommendations servicing Sydney? I am aware of Hammond, and can trawl the usual Aliexpress and Ebay.
Any shared experiences welcome including pitfalls to avoid?
What determines the working voltage for secondary's heater output and supply for B+?
Are you asking how I choose these Voltages, or how to achieve them when designing.. or how it might be done in your case?
I remember seeing a paper from Uni NSW on this subject, let me see if I can find it.
Hare it is: LV Voltage Report | Energy Council
Makes you wonder if it would be better to design for a grid voltage of 245 - 250v instead of the usual 230v standard when:
Hare it is: LV Voltage Report | Energy Council
Makes you wonder if it would be better to design for a grid voltage of 245 - 250v instead of the usual 230v standard when:
Philip, I'd suggest a bucking transformer (that drops 10-15V) is a better outcome than a variac for a fixed appliance. A Variac can accidentally go up or down, and would have noticeably more magnetising current and in-rush.
The key target is the loaded heater sitting at 6.3V within 5%.
Your smart meter is a more recent model than mine, and they have programmed QoS parameters for display which is nice indeed.
The key target is the loaded heater sitting at 6.3V within 5%.
Your smart meter is a more recent model than mine, and they have programmed QoS parameters for display which is nice indeed.
Yes, I've not extensively searched but it seems a few stock transformers go to 230V and the bulk are 110/220V. Ideally, multiple secondary taps between 220V to 250V & 6.3V. Perhaps this requires a custom build.