Tantalum capacitor value and type - UK Vintage Radio Repair and Restoration Discussion Forum

Levente · 6th Jul 2019, 6:32 pm

Hey Guys!

Hope you are all well. Glad to be back and start a thread again...this time as I am not familiar with military grade coding of tantalum cap's, I was hoping some of you can help me identify this...I have tried Google the good friend, but I would rather trust this forum and your experience and knowledge..

I have a rather expensive unit from 1971 and I do not want to solder or de solder parts unnecessarily.

The PCB is at the PSU, providing 15+, -15 and a 5V DC

I have there several extremely large Mallory caps (big as my coffee mug) all within specs and several ( this is the one I am unsure):

TANTALUM caps and codes on this CS13B E476K.

No further markings with regards the voltages, the farad's or anything.

I found similar coding caps on Farnell and Mouser however I am not 100% certain on this..

Could you please point me in to the right drection?

476k means 47.6 Uf? and I can assume as no more than 15 VDC is generated on this section of the PCB I am safe with 20V ratings?

Many thanks for your help !

julie_m · 6th Jul 2019, 7:09 pm

476K more probably means 47 and 6 zeros pF, i.e. 47μF, with the K signifying +/-20%.

Old tantalum capacitors can usually be replaced with modern electrolytics; which, due to improvements in capacitor manufacturing in the meantime, are almost always as good or better in terms of both parameters (ESR, leakage .....) and size than the original tantalum ones.

jamesperrett · 7th Jul 2019, 1:04 am

Don't be tempted to go any lower than 20V as the working life will be much reduced if used close to their rated voltage.

Levente · 7th Jul 2019, 7:46 am

Thanks guys... really appreciate it. There are 18 axial quiet large tantalum capacitors in here some of them are in series. I know you are not suppose to measure in circuit, however, as I am having this Peak ESR capacitor tester which advertised to measure capacitance and ESR in circuit, thought will give me a good indication....most of the caps are 3 times above the 47uF but the ESR is really low still...and some of them are "leaky" according to the device but again ESR are 0,17 or so...am I getting misinformed here by this device? Just wondered...

Craig Sawyers · 7th Jul 2019, 8:10 am

Are there charge balancing resistors across each of the series-connected tantalums?

Craig

Levente · 7th Jul 2019, 8:11 am

Quote:

Originally Posted by Craig Sawyers

Are there charge balancing resistors across each of the series-connected tantalums?

Craig

Thank you !

Let me take a picture Craig..i think there are some... will get back to you asap.

Levente · 7th Jul 2019, 8:39 am

Quote:

Originally Posted by Craig Sawyers

Are there charge balancing resistors across each of the series-connected tantalums?

Craig

in total I have 22 these types of Tantalum caps. Few at the 5V and 15V PSU board and the rest are on the other delay unit PCB and the signal input/ output PCB.....

MrBungle · 7th Jul 2019, 9:00 am

Those are military spec wet tantalum capacitors. Unless any are short I’d leave them be.

Problem with them is you can’t get decent low ESR axial capacitors to replace them leaving only bodges or buying originals as the outcome

The replacements cost £8-20 each (!) in low quantities.

Some of them were chosen because the self resonant frequency is far higher than the average electrolytic. You can usually get away with pushing that up by using a low ESR electrolytic with a ~100nF X7R MLCC across it.

Levente · 7th Jul 2019, 9:08 am

Thanks for the advice. would you trust the Peak ESR when it says "in-circuit leaky" or I should de-solder, check individually and re solder if it is within specs? (I assume the desoldering is the way to go...?)

MrBungle · 7th Jul 2019, 9:23 am

On wet tants I usually just check them with a DMM. Resistance is usually <10 ohms if they are dead. Also fire up the board and check the temperature. The failing ones run warm.

I’ve got a homebrew ESR meter but I only use that on electrolytics.

Levente · 7th Jul 2019, 9:37 am

Awesome. Thaks a lot!

Most of them measures identical 101 Ohms.

However, there some, measuring 400 Ohms and some measures 18 kOhms...these are always the one of the "in-series" ones usually, next to each other..

At the PSU there is a single one measuring 460 Ohms and two next to each other measuring 460 Ohm and the next one 1200 kOhms...

Are these high values concerning?

MrBungle · 7th Jul 2019, 9:40 am

You’re measuring the impedance of the power supply there. The exceptional value is usually below 10 ohms ie there is a capacitor which is a lower impedance than the supply. Everything else above that is ok.

Edit: on the age of the capacitors I have a couple of HP power supplies from the late 1960s and they have the same parts in them and they’re still good

Levente · 7th Jul 2019, 9:45 am

Thanks! That means all of these cap's including next to the PSU seems to be OK so far and I can actually plug the unit in for further testing?

Next will be voltages I guess...to check if everything is OK and getting 15+, -15 and 5 VDC.

By the way the unit is a Lexicon Delta T 102-B delay module.

Could you please advise how to remove dirt and dust of these PCBs with full of ICs? I do not want to cause electrical damage to these ICs with some static cloth or something...

Craig Sawyers · 7th Jul 2019, 10:54 am

Take the board out and wash it in warm water with a bit of soap (Fairy or similar), using a paintbrush to get into the crannies. Rinse well and put in the airing cupboard.

Sounds brutal, but Tektronix service centres used to do that with an entire mainframe scope - either valve or semiconductor - before even powering it up for diagnostics. They did not take socketted semiconductors or valves out before doing that.

See attachment. One of the key old boys from Tektronix, made his own drying chest for his collection of mainframe scopes using an old chest freezer, fans to circulate air, and a small heater to warm the air.

Craig

Levente · 7th Jul 2019, 11:06 am

HOLY CRAP! I am scared of this...a bit tho..but

Thank you so much for this, will try and give a gentle wash with a sponge. It is not extremely dirty, but more dusty...

many thanks for this!

Craig Sawyers · 7th Jul 2019, 11:19 am

I have not personally washed a whole scope. But I take out the upward facing boards out (in particular the horizontal amplifier in 7000 series scopes which is under ventilation holes and gets absolutely filthy) and do the warm water and paintbrush trick. They come up looking like new and always work perfectly.

First time I did this was our colour TV back in the early 80's. It was underneath a hanging plant, and one day after watering it too generously it poured water into the back of the TV, which fortunately was switched off. Off came the back, unplugged the circuit boards and put them in the oven (my wife was horrified) at 60C until they dried out. Reassembled - perfect working order.

Craig

Levente · 7th Jul 2019, 11:38 am

Hahaha, that is great. Thanks Craig, will do this trick later. This machine is insanely built...believe to be the first ever digital reverb/delay designed from 1971 at Gotham Audio and assembled in 1974 onwards by LExicon...built like a tank. Every single part, the soldering the capacitors, the whole design is just flawless...wonder what it can do...

Cheers!

6th Jul 2019, 6:32 pm	#1
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Tantalum capacitor value and type Hey Guys! Hope you are all well. Glad to be back and start a thread again...this time as I am not familiar with military grade coding of tantalum cap's, I was hoping some of you can help me identify this...I have tried Google the good friend, but I would rather trust this forum and your experience and knowledge.. I have a rather expensive unit from 1971 and I do not want to solder or de solder parts unnecessarily. The PCB is at the PSU, providing 15+, -15 and a 5V DC I have there several extremely large Mallory caps (big as my coffee mug) all within specs and several ( this is the one I am unsure): TANTALUM caps and codes on this CS13B E476K. No further markings with regards the voltages, the farad's or anything. I found similar coding caps on Farnell and Mouser however I am not 100% certain on this.. Could you please point me in to the right drection? 476k means 47.6 Uf? and I can assume as no more than 15 VDC is generated on this section of the PCB I am safe with 20V ratings? Many thanks for your help !

6th Jul 2019, 7:09 pm	#2
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Tantalum capacitor value and type 476K more probably means 47 and 6 zeros pF, i.e. 47μF, with the K signifying +/-20%. Old tantalum capacitors can usually be replaced with modern electrolytics; which, due to improvements in capacitor manufacturing in the meantime, are almost always as good or better in terms of both parameters (ESR, leakage .....) and size than the original tantalum ones. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

7th Jul 2019, 1:04 am	#3
jamesperrett Octode Join Date: May 2007 Location: Liss, Hampshire, UK. Posts: 1,876	Re: Tantalum capacitor value and type Don't be tempted to go any lower than 20V as the working life will be much reduced if used close to their rated voltage.

7th Jul 2019, 7:46 am	#4
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Re: Tantalum capacitor value and type Thanks guys... really appreciate it. There are 18 axial quiet large tantalum capacitors in here some of them are in series. I know you are not suppose to measure in circuit, however, as I am having this Peak ESR capacitor tester which advertised to measure capacitance and ESR in circuit, thought will give me a good indication....most of the caps are 3 times above the 47uF but the ESR is really low still...and some of them are "leaky" according to the device but again ESR are 0,17 or so...am I getting misinformed here by this device? Just wondered...

7th Jul 2019, 8:10 am	#5
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,993	Re: Tantalum capacitor value and type Are there charge balancing resistors across each of the series-connected tantalums? Craig

7th Jul 2019, 9:00 am	#8
MrBungle Dekatron Join Date: Jun 2016 Location: London, UK. Posts: 3,687	Re: Tantalum capacitor value and type Those are military spec wet tantalum capacitors. Unless any are short I’d leave them be. Problem with them is you can’t get decent low ESR axial capacitors to replace them leaving only bodges or buying originals as the outcome The replacements cost £8-20 each (!) in low quantities. Some of them were chosen because the self resonant frequency is far higher than the average electrolytic. You can usually get away with pushing that up by using a low ESR electrolytic with a ~100nF X7R MLCC across it.

7th Jul 2019, 9:08 am	#9
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Re: Tantalum capacitor value and type Thanks for the advice. would you trust the Peak ESR when it says "in-circuit leaky" or I should de-solder, check individually and re solder if it is within specs? (I assume the desoldering is the way to go...?)

7th Jul 2019, 9:23 am	#10
MrBungle Dekatron Join Date: Jun 2016 Location: London, UK. Posts: 3,687	Re: Tantalum capacitor value and type On wet tants I usually just check them with a DMM. Resistance is usually <10 ohms if they are dead. Also fire up the board and check the temperature. The failing ones run warm. I’ve got a homebrew ESR meter but I only use that on electrolytics.

7th Jul 2019, 9:37 am	#11
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Re: Tantalum capacitor value and type Awesome. Thaks a lot! Most of them measures identical 101 Ohms. However, there some, measuring 400 Ohms and some measures 18 kOhms...these are always the one of the "in-series" ones usually, next to each other.. At the PSU there is a single one measuring 460 Ohms and two next to each other measuring 460 Ohm and the next one 1200 kOhms... Are these high values concerning?

7th Jul 2019, 9:40 am	#12
MrBungle Dekatron Join Date: Jun 2016 Location: London, UK. Posts: 3,687	Re: Tantalum capacitor value and type You’re measuring the impedance of the power supply there. The exceptional value is usually below 10 ohms ie there is a capacitor which is a lower impedance than the supply. Everything else above that is ok. Edit: on the age of the capacitors I have a couple of HP power supplies from the late 1960s and they have the same parts in them and they’re still good

7th Jul 2019, 9:45 am	#13
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Re: Tantalum capacitor value and type Thanks! That means all of these cap's including next to the PSU seems to be OK so far and I can actually plug the unit in for further testing? Next will be voltages I guess...to check if everything is OK and getting 15+, -15 and 5 VDC. By the way the unit is a Lexicon Delta T 102-B delay module. Could you please advise how to remove dirt and dust of these PCBs with full of ICs? I do not want to cause electrical damage to these ICs with some static cloth or something... Last edited by Levente; 7th Jul 2019 at 9:47 am. Reason: missing info

7th Jul 2019, 11:06 am	#15
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Re: Tantalum capacitor value and type HOLY CRAP! I am scared of this...a bit tho..but Thank you so much for this, will try and give a gentle wash with a sponge. It is not extremely dirty, but more dusty... many thanks for this!

7th Jul 2019, 11:19 am	#16
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,993	Re: Tantalum capacitor value and type I have not personally washed a whole scope. But I take out the upward facing boards out (in particular the horizontal amplifier in 7000 series scopes which is under ventilation holes and gets absolutely filthy) and do the warm water and paintbrush trick. They come up looking like new and always work perfectly. First time I did this was our colour TV back in the early 80's. It was underneath a hanging plant, and one day after watering it too generously it poured water into the back of the TV, which fortunately was switched off. Off came the back, unplugged the circuit boards and put them in the oven (my wife was horrified) at 60C until they dried out. Reassembled - perfect working order. Craig

7th Jul 2019, 11:38 am	#17
Levente Hexode Join Date: Nov 2016 Location: Budapest, Hungary Posts: 386	Re: Tantalum capacitor value and type Hahaha, that is great. Thanks Craig, will do this trick later. This machine is insanely built...believe to be the first ever digital reverb/delay designed from 1971 at Gotham Audio and assembled in 1974 onwards by LExicon...built like a tank. Every single part, the soldering the capacitors, the whole design is just flawless...wonder what it can do... Cheers!