Small diameter electrolytics for Walkman repair - Page 1
Forum section: electronics / repair

author: egenjohn
author_rank: Newbie
timestamp: August 23, 2025, 11:24:49 pm
content: I'm working on repairing an old Walkman (WM-FX70). The two 330u electrolytic caps have gone bad in it reading only a couple of n. Not usually a problem, but these caps are only 4mm in diameter and I haven't been able to find replacements. The size is important, even a 5mm won't fit in the tight space. I thought I'd check the best electronics forum to see if anyone has suggestions on sourcing replacements.My next option is to maybe put leads on a SMD organic polymer cap. But I've never worked with them before and don't know if there are going to be any gotchas going this route.

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: August 24, 2025, 12:51:49 am
content: It may seem funny but Sony parts, from Sony the service manual will have the part numbers and they might still be available.Jeff

author: amyk
author_rank: Super Contributor
timestamp: August 24, 2025, 02:22:52 am
content: We would be able to try finding a suitable replacement if you gave the rest of the specs besides their diameter.

author: Simmed
author_rank: Frequent Contributor
timestamp: August 24, 2025, 05:49:05 am
content: the biggest SMD ecap 4mm dia i can see on mouser is 100uF

author: temperance
author_rank: Super Contributor
timestamp: August 24, 2025, 08:55:20 am
content: Are you just re-capping the walkman because it is fancy re-recap old equipment?Can you post a picture? 330 might not mean what you think it means.EDit:Two minutes searching the web I found the service manual. No 330 µF capacitors can be found in component list.The largest capacitor seems to be: C301, TANTAL. CHIP, 47uF, 20%, 2.5VSo you are just recapping a walkman because it is fancy to re-cap stuff... The capacitors you want to replace (and probably any other capacitor) are probably all just fine.Is this your own walkman?

author: egenjohn
author_rank: Newbie
timestamp: August 24, 2025, 02:54:33 pm
content: Here's a photo of the caps in question. Just 330uF, 2V electrolytic caps in a very small package. I haven't been able to find anything based on the Sony part number. But if you're following along at home the caps in question are C118 and C218. They're connected to pins 11 and 13 of IC304, the headphone power amp.

author: Zoli
author_rank: Frequent Contributor
timestamp: August 24, 2025, 11:27:52 pm
content: Quote from: egenjohn on August 24, 2025, 02:54:33 pmI hate myself for this advice, but: you can get MLCC's in 1210(3.2X2.5mm) case rated 330µF/4V like this:https://www.digikey.ca/en/products/detail/murata-electronics/GRM32ER60G337ME05L/6155746It will work, but consider it as a temporary solution, since it will add distortions because of the non-linearities(C->V,C->f).Forget what I've said above; you can get tantalum, tantalum-poly or Al-poly SMD capacitors which can be fit in the available space:Ta:https://www.digikey.ca/en/products/detail/kyocera-avx/F930G337MCC/4005350Ta-poly:https://www.digikey.ca/en/products/detail/kemet/T520B337M006ATE070/9558195Al-poly:https://www.digikey.ca/en/products/detail/panasonic-electronic-components/EEF-CX0E331R/1731672

author: egenjohn
author_rank: Newbie
timestamp: August 25, 2025, 12:47:51 am
content: Thanks Zoli. The Tantalums I saw on Mouser were too tall, but these look perfect.

author: amyk
author_rank: Super Contributor
timestamp: August 25, 2025, 01:58:04 am
content: Be careful with tantalums, they are not a drop-in replacement for aluminium electrolytics and need significant voltage derating.

author: MathWizard
author_rank: Super Contributor
timestamp: August 25, 2025, 02:21:47 am
content: IDK they made such low voltage caps, but I guess they might be cheaper if they use a thinner or worse insulator layer.

author: Zoli
author_rank: Frequent Contributor
timestamp: August 25, 2025, 06:20:46 am
content: Quote from: amyk on August 25, 2025, 01:58:04 amOriginal cap is rated for 2V; the linked caps: Ta rated for 4V, Ta-poly 6.3V, Al-poly 2.5V.@MathWizard: no need for higher voltage ratings, when the electronics is running on 0.8-1.5V(CPU, GPU, FPGA, even some micros).

author: temperance
author_rank: Super Contributor
timestamp: August 25, 2025, 04:09:42 pm
content: I found the correct service manual. Those caps seem to be the headphone AC coupling capacitors.QuoteThose have very high leakage current in the range of a few 100 µA up to maybe a 500 µA and will probably drive the very sensitive headphone into "saturation" and eventually drain the battery while the unit is not playing if the amplifier is not shut down.https://industrial.panasonic.com/cdbs/www-data/pdf/AAB8000/AAB8000C179.pdfBut something like this might work:https://www.mouser.be/ProductDetail/Samsung-Electro-Mechanics/CL32X337MSVN4SE?qs=ST9lo4GX8V1SwbOuK926pg%3D%3DOr three or four of those in parallel (330 µF with 16 R= - 3 dB at around 30 Hz.):https://www.mouser.be/ProductDetail/TDK/C4532X5R0J107M280KA?qs=NRhsANhppD8FGACq1Q9ZSA%3D%3D

author: Zoli
author_rank: Frequent Contributor
timestamp: August 26, 2025, 06:45:25 am
content: Quote from: temperance on August 25, 2025, 04:09:42 pmI wouldn't recommend using X5-X6 ceramic capacitors in the audio path; they can add significant distortion. See my previous post for a typical voltage-capacitance diagram.

author: temperance
author_rank: Super Contributor
timestamp: August 26, 2025, 12:56:35 pm
content: I found some real data from TI:https://www.ti.com/lit/an/slyt796a/slyt796a.pdf?ts=1756134849301A large X5R 47 µF 16 V capacitor has a THD below -80 dB for frequencies above 20 Hz. Not bad.

author: Zoli
author_rank: Frequent Contributor
timestamp: August 27, 2025, 06:30:05 am
content: Quote from: temperance on August 26, 2025, 12:56:35 pmOn a 2.5kΩ load; try to estimate for 16Ω, which is the typical headphone impedance for those Walkmans; my estimate is -40dB, which translates to 1%. But anyway, why one should use a non-linear component, when a linear is available?

author: temperance
author_rank: Super Contributor
timestamp: August 27, 2025, 10:53:52 am
content: QuoteThe leakage current of those "linear" capacitors is way too high, with 0.5 mA.

author: Zero999
author_rank: Super Contributor
timestamp: August 27, 2025, 11:47:06 am
content: Those appear to be custom made.Perhaps a tantalum SMT connected in a radial with bodge wires and covered in epoxy.Something like this?https://www.digikey.co.uk/en/products/detail/kyocera-avx/F950J337KBAAQ2/4005418Not nice I know.

author: Zoli
author_rank: Frequent Contributor
timestamp: August 28, 2025, 01:54:38 am
content: Quote from: temperance on August 27, 2025, 10:53:52 amIn this case, let's take a look what "too high" means besides the power consumption. For simplicity, let's suppose that the Walkman provides 2.8Vppon the output into the 16Ω headphones; that means (2.8/2)/16=87.5mA peak. Let's suppose that the 87.5mA saturates the headphone, so without distortion it can accept only 87mApeak. 20*log(87/87.5)=-0.049776dB. Summing it up: in worst case, 0.5mA leakage ends up in 0.049776dB loss in the peak SPL. Of course, if the OP sticks to the Tantalum capacitors, the linked one has only 5µA leakage in this application; as homework, calculate the dB loss for that case.Follow-up on ceramic capacitors: it would be really interesting to see inter-modulation measurements on X7/5R capacitors, since the byproducts(=distortion) thrive on non-linearities.