Use 2SC2904(Produecd by HG) to Repair my IC725

This material comes from "Hello CQ Forum".(Refer to following link)

http://www.hellocq.net/forum/showthread.php?t=280576&page=1&pp=30

I heard for years that a company produces various models of the launch tube, that is the price is very cheap. Over the past few years I design and development of the HF transceiver kit is also many, for lower cost considerations have been using IRF530640 or HEXFET pipe to make the launch tube. Although the effect is also good, but the heart is also very much hope to use professional launch tube. In the QQ group chat with everyone up power, no brakes, brain hyperemia decided to buy several pipe back to try.

Now do power amplifier board is late, then playing the IC725's idea. Because a lot of ICOM radio station in 2SC2904 make use of power tube, on Taobao out 2904 cheaper than imported cheap too much, I remember the original imported 2904 to nearly 300 yuan one. Then 2 days later, received 4 domestic 2SC2904.

Just trying to get 725 of the power amplifier apart, the year of machine design was long, remove the power amplifier is very troublesome.

It's 100 blocks of one only three transistors, I never had such an expensive new three transistors, although is made in china. The new pipe, tube feet bright polished tile.

According to IC725 repair manual, power level of the quiescent current, should be in 300mA. I don't know why, I the machine always in 120mA, in any case also did not transfer to 300mA. Using the original tubes as well, don't know is it right? Have a problem.

Test results, let me by surprise. Domestic 2SC2904 725 can work each band in the output power was to achieve 100 W, and there is no difference between the original pipe. When according to the forum 725 lover introduction method, adjustable power can reach 120 ~ 130 watts. Only for the domestic pipe resistance exercise capacity lack of confidence, finally in 100 watts. Try on several radio, continue for more than 1 hours, the machine temperature and output power are very stable.

Testing this, I feel very accidentally, also feel very excited. This tube is very inexpensive, 100 watts of output power, only need to increase the cost of 200 yuan.

I also learnd from a friend that he use HG 2SC2904 to repair ICOM 700PRO. The transistor works also well.

年前就聽說過無錫有一家公司生產各種型號的發射管，說是價格很便宜。但也有人說這家的管子容易壞，加上對國產這類器件多少也帶著點不信任的情緒，所以一直也就沒太過多的關注。

這幾年我設計開發的短波收發信機套件也是不少了，出于降低成本的考慮一直都在使用IRF530，640之類的HEXFET管子做發射管。雖然效果也還不錯，但是憑心而論也是十分希望用一用專業發射管。在QQ群里和大家聊起來功放，沒剎住車，頭腦充血決定買幾只管子回來試試。真不行的話，也就損失幾百塊錢，也讓我死了心罷！

現做功放板是來不及了，于是打起了IC725的主意。因為ICOM很多電臺都在使用2SC2904做功率管，上淘寶一查2904的價格是100元。這可比進口的便宜太多了，我記得原裝進口的2904要將近300元一只。于是2天后，收到了4只國產的2SC2904。